Biology B6 (Inheritance, variation and evolution)

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what is a somatic cell?
a body cell
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what is another word for a somatic cell?
diploid cell (46 chromsomes)
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what is a gamete also called?
haploid cell (23 chromosomes)
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Does meiosis lead to identical or non-identical cells being formed?
Non-identical
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Does mitosis lead to identical or non-identical cells being formed?
Identical
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What does sexual repoduction involve?
The fusion of male an female gametes
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What are the gametes in animals?
sperm and egg cells
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What are the gametes in planta?
pollen and egg (ovum) cells
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In what type of reproduction is there a mixing of genetic information which leads to variety in the offspring?
Sexual
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What does the formation of gametes involve?
Meiosis
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How many parents are there in asexual reproduction?
1
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Are gametes fused in asexual reproduction?
No
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What does this mean about the variation of the offspring?
That there is no mixing of genetic information leading to genetically identical offspring(clones)
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What type of cell division is involved in asexual reproduction?
Mitosis
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What is made a cell divides to form gametes?
Copies of the genetic informtion
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In this process, how many times does the cell divide and how many gametes are formed with how many chromosomes with it?
The cell divides twice to from four gametes, each with a single set of chromosomes
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Are all gametes genetically similar or different to each other?
They are genetically different
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By what process do gametes join at to restore the normal number of chromosomes
Fertilisation
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By what division does this new cell divide by to increase the number of cells?
Mitosis
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explain why sexual reproduction could produce a new variety of plant (3 marks)
fusion of gametes, leading to a mixing of genetic information, ONE copy of each gene from each parent
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What are the advantages of sexual reproduction?
Produces variation in the offspring, this variation gives a survival advantage by natural selection if the environment changes, can be sped up by humans in selective breeding to increase food production
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What are the advantages of asexual reproduction?
Only one parent needed, more time/eneegy efficient as don't have to find a mate, faster than sexual, many identical offspring an be produced if they are good conditions
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]Where do malarial parasites reproduce asexually?
Inside the human host
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Where do malarial parasites reproduce sexually?
In the mosquito
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How do fungi reproduce asexually by?
Spores
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Why do fungi reproduce sexually?
To give variation
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how do many plants reproduce?
Sexually
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Which plants produce asexually and by what ?
strawberry plants by runners and daffodils by bulb division
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Where in the cell is the genetic information stored?
In the nucleus
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What is the chemical inside the nucleus that contains the genetic material called?
DNA
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What structure is DNA?
a polymer
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What is DNA made up of and what does this form?
two strands which forms a double helix
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What are the structures that DNA is contained in?
Chromosomes
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What is a gene?
A small section of DNA on a chromosome
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What does each gene code for a particular sequence of, and what does this make?
Codes for a particular sequence of amino acids, to make a specific protein
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What is a genome of an organism?
The entire genetic material of that organism
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What is DNA made from (there's four of them)?
Four different nucleotides
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What does each nucleotide consist of?
A sugar, a phosphate and one of four different bases attached to the sugar
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What are the four bases of DNA (in letters)
A, C, G, T
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Which pairs of bases always bind together?
C and G, A and T
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A sequence of how many bases is the code for a particular amino acid?
Three
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What does the order of these bases control?
The order in which amino acids are assembled to produce a particular protein
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What do the bases attach to?
A sugar
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What is the backbone of a strand of DNA called?
The sugar-phosphate backbone
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Where are proteins synthesised?
In ribosomes
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What bring specific amino acids to add to the growing protein chain in the correct order?
carrier molecules
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Where are the carrier molecules made?
In the cell membrane
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What are carrier molecules?
Molecules that are genetically identical to the specifc gene inside the ribosmes however thsi geen cannot leave so a carrieer molecule is produced to transport the particular sequence of amino acids?
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What happens when the protein chain is complete?
It folds up to form a unique shape
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What jobs can proteins do now they have their unique shape?
Enzymes, hormones or forming structures in the body such as collagen
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What is a mutation?
A change in a gene or chromosome
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Do mutations alter/ change the appearance or function of a protein?
No
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What do a few mutations code for?
An altered protein with a different shape
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What may happen because of this?
An enzyme may no longer fit the substrate binding site or a structural protein may lose its strength
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Do all parts of DNA code for proteins?
No
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What can these non-coding parts of DNA do?
They can switch genes on and off, so variations in these areas of DNA may affect how genes are expressed
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What is an allele?
different versions of the same gene
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What is an organism's genotype?
The collection of alleles that determine an organism's characteristics such as the genes that determine eye colour
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What is an organism's phenotype?
A particular version of a characteristic seen in an individual such as eye colour
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What is a dominant allele?
One that is always expressed, even if one copy is present
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What is a recessive allele?
One that is only expressed if two copies are present/ at the absence of the dominant allele
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What does mean if an organism is homozygous for a certain trait?
If two alleles are present that are the same
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What does mean if an organism is heterozygous for a certain trait?
If the alleles are different
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What is an example of an inherited disorder caused by a dominant allele?
Polydactyly (having extra fingers or toes)
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What is an example of an inherited disorder caused by a recessive allele?
Cystic fibrosis (a disorder of the cell membrane)
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How many pairs of chromosomes are there in an ordinary human cell?
23
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In what two types of cell in the body would you find less/no chromosomes?
In gametes as they have 23 chromosomes and in red blood cells as they have no nucleus to contain the chromosomes
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give 3 arguments against embryo screening
increase prejudice (implies ppl with genetic problems are undesirable), expensive, ppl may want to screen their embryo in IVF to pick the most desired one
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give 3 arguments for embryo screening
helps people to stop suffering from genetic disorders, reduces no. ppl with disorders could save money, there are laws to stop parents from selecting desirable characteristics for their baby
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In these 23 pairs of chromosomes, how many pairs control characteristics?
22
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How many pairs carry the gene that determines sex?
1
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What are the sex chromosomes in females?
**
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What are the sex chromosomes in males?
XY
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How is the dominant allele expressed?
By a capital letter e.g. R
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How is the recessive allele expressed?
By a lowercase version of that same letter e.g. r
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What is variation?
The differences in the characteristics of individuals in a population
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What could be the cause of variation?
genes they have inherited (genetic causes), the conditions in which they have developed (environmental causes), and a combination of genes and the environment
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What is evolution?
A change in the inherited characteristics of a population over time though a process of natural selection which may result in the formation of a new species
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What does the theory of evolution by natural selection state?
That all species of living things have evolved from simple life forms that first developed more than three billion years ago.
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If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring what have they formed?
two new species
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What is selective breeding also known as?
Artificial selection
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What is selective breeding?
the process by which humans breed plants and animals for particular genetic characteristics
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Why have humans been doing this for thousands of years?
They needed to breed food crops form wild plants and domesticated animals as pets
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What does selective breeding involve?
choosing parents with the desired characteristic from a mixed population, they then breed together, then the offspring with this desired characteristic are then bred.
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what are examples of selective breeding being used for usefulness?
Disease resistance in food crops, animals which produce more meat or milk
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what are examples of selective breeding being used for appearance?
Domestic dogs with a gentle nature, large or unusual flowers
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What could selective breeding lead to?
Inbreeding
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What is inbreeding?
where some breeds are particularly prone to disease or inherited defects
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What is genetic engineering?
a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
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Why have plant crops been genetically engineered?
To be resistant to diseases or to produce bigger, better fruits
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What have bacterial cells been genetically engineered to produce?
human insulin
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What disease does insulin treat?
Type 2 diabetes
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What are crops that have had their genes modified by genetic engineering called?
GM (genetically modified) crops
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what are the benefits of genetic engineering?
is a faster/more efficient way of getting the same results as selective breeding, improves crop yields/quality, introduces herbicide resistance, insect/pest resistance can be developed and inserted into the plants, sterile insects could be created
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what are the risks of genetic engineering?
transfer of the selected gene into other species, some believe it isn't ethical to interfere with nature this way, GM crop seeds are more expensive, could be harmful, could cause allergic reactions in people
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what is tissue culture? (plants)
using small groups of cells from part of a plant to grow identical new plants
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what are cuttings? (plants)
an older, but simple, method used by gardeners to produce many identical new plants from a parent plant.
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what do embryo transplants involve? (animals)
splitting apart cells from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers.
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What type of cell division takes place in cloning?
mitosis
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What are the 4 types of cloning?
tissue culture, cuttings, embryo transplants, adult cell cloning
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what does adult cell cloning involve? (animals)
The nucleus is removed from an unfertilised egg cell. • The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell. • An electric shock stimulates the egg cell to divide to form an embryo.
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part 2
These embryo cells contain the same genetic information as the adult skin cell. • When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development.
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What has the available evidence for Darwin's theory shown?
That characteristics are passed on to offspring in genes
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What 2 other places is there further evidence for this?
fossil records, knowledge of resistance to antibiotics evolves in bacteria
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What are fossils?
'remains' of organisms from millions of years ago, which are found in rocks
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What are the 3 ways in which fossils may be formed?
from parts of organims that haven't decayed as one or more condtions for decay are absent, parts of organism are replaced by minerals as they decay, as preserved traces of organisms, like footprints burrows and rootlet
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is there little or lots left behind of soft-bodied organisms?
little
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What were these traces destroyed by?
geological activity (earthquakes, volcanoes)
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What can fossils provide evidence for?
evolution
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Why?
As it shows how species have had their characteristics changed to become more suited to their environment
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Card 2

Front

what is another word for a somatic cell?

Back

diploid cell (46 chromsomes)

Card 3

Front

what is a gamete also called?

Back

Preview of the front of card 3

Card 4

Front

Does meiosis lead to identical or non-identical cells being formed?

Back

Preview of the front of card 4

Card 5

Front

Does mitosis lead to identical or non-identical cells being formed?

Back

Preview of the front of card 5
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