Genetics and Selection

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  • Created by: rachmhw
  • Created on: 19-04-19 12:43
what is inheritance?
the transmission of genetic information from generation to generation
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what is a chromosome?
a threadlike structure of DNA, carrying genetic information in the form of genes
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what is a gene?
a length of DNA that codes for a protein Define allele as a version of a gene
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how do humans inherit their gender?
23rd pair of chromosomes are the sex chromosomes, women have two X chromosomes, men have one X and one Y
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what is the chance of being a boy or a girl?
50%
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what is genetic code?
information carried in DNA in the form of a code
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what bases make up genetic code?
A, T, C, G
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what are proteins made from?
amino acids
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what determines the function of the protein?
the sequence of the amino acids determined by the sequence of bases in a DNA molecule
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what are examples of protein functions?
enzymes, antibodies, receptors for neurotransmitters
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how are proteins made?
gene coding for the protein remains in the nucleus/mRNA molecules carry a copy of the gene to the cytoplasm/goes to ribosomes/ribosome assembles amino acids into protein molecules of order of the bases
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where is DNA found?
in the nucleus
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where does protein synthesis occur?
in the ribosomes in the cytoplasm
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what does mRNA / messanger RNA do?
copies the base sequence for the production of a protein
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what do all cell contain?
the same genes
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what does gene expression mean?
not all genes are expressed because the cell only makes the specific proteins it needs
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what is a haploid nucleus?
a nucleus containing a single set of unpaired chromosomes, e.g. in gametes
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what is a diploid nucleus?
a nucleus containing two sets of chromosomes, e.g. in body cells
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what is the diploid number of cells in humans?
23 pairs, 46 chromosomes
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what is an allele?
a version of a gene
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what is mitosis?
s nuclear division giving rise to genetically identical cells
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what is meiosis?
s nuclear division giving rise to cells that are genetically different
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what is mitosis used for?
growth, repair of damaged tissues, replacement of cells and asexual reproduction
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what happens before mitosis occurs?
exact duplication of chromosomes
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what happens during mitosis?
the copies of chromosomes separate, maintaining the chromosome number
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what are stem cells?
specialised cells that divide by mitosis to produce daughter cells that can become specialised for specific functions
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what is meiosis used for?
used for making gametes
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what is happens during meiosis?
reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
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what are the steps during meiosis?
chromosomes are copied, 2 chromosomes in the pair separate, daughter cell divides again = 4 haploid cells
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why does meiosis create variety?
only half of the parent cell is passed on to the nucleus of the daughter cell AND forming new combinations of maternal and paternal chromosomes
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what is the genotype?
the genetic make-up of an organism in terms of the alleles present
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what is phenotype?
the observable features of an organism
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what is homozygous?
having two identical alleles of a particular gene
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what will happen if 2 homozygous individuals breed?
they be pure-breeding
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what is heterozygous?
having two different alleles of a particular gene
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will heterozygous individuals pure-breed?
no
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what is a dominant allele?
an allele that is expressed if it is present
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what is a recessive allele?
s an allele that is only expressed when there is no dominant allele of the gene present
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what does a pedigree diagram show?
its is a chart showing the phenotypes of individuals in a family over several generations
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what is co-dominance?
when neither allele is dominant or recessive, they both have an affect on the heterozygous individual
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what are examples of co-dominance?
human blood groups
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what are the phenotypes of human blood groups?
A, B, AB and O
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when is blood group A produced?
with I A and I A or I A and I B
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when is blood group B produced?
I B and I B or I B and I O
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when is blood group AB produced>
I A and I B
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when is blood group O produced?
I O and I O
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what is a sex-linked characteristic?
a characteristic in which the gene responsible is located on a sex chromosome and that this makes it more common in one sex than in the other
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what is an example of a sex-linked characteristic?
colour-blindness
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what is varitaiton?
differences between individuals of the same species
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what is the difference between phenotypic variation and genetic variation?
genetic variation may not change the phenotype (e.g. Bb and BB have same phenotype) also genotypes can be changed by environment
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what can cause variation in individuals?
their genes, the environment
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what is continuous variation?
a range of phenotypes between two extremes, e.g. height in humans
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what is discontinuous variation?
variation results in a limited number of phenotypes with no intermediates, e.g. tongue rolling
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what kind of graph is used for continuous variation?
a histogram
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what kind of graph is used for discontinuous variation?
a bar chart
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what is a mutation?
a genetic change/ it is the way in which new alleles are formed / a change in the base sequence of DNA
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what causes phenotypic variation?
by both genetic and environmental factors
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what causes discontinuous variation?
mostly caused by genes alone
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what can increase the risk of mutation?
some chemicals and by ionising radiation
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what are the symptoms of sickle-cell anaemia?
breathlessness as haemoglobin can't transport oxygen properly
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what causes sickle-cell anaemia?
an allele of a gene that has a changed base sequence = haemoglobin with wrong amino acid sequence = can't transport oxygen properly
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what are the alleles for someone without sickle-cell?
Hb^A and HB^A
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what are the alleles for someone with sickle-cell?
HB^S and HB^S
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what is an advantages of being a carrier of sickle-cell anaemia?
they are resistant to malaria
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how does sickle-cell anaemia benefit people in an areas with malaria?
children who are carriers will survive and have children = children may inherit sickle cell allele
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how does sickle-cell anaemia disadvantage people in an areas without malaria?
blood doesn't carry oxygen well, so without sickle-cell anaemia = survive to adulthood = children won't inherit sickle-cell anaemia
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what is an adaptive feature?
an inherited functional feature that helps an organism to survive and reproduce in its environment and increase its fitness
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what is fitness?
the probability of an organism surviving and reproducing in the environment in which it is found
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what are the adaptive features of hydrophytes?
stomata on top of leaf - CO2 and O2 can diffuse from the air AND leaves with large surface area - can float and get sunlight AND air spaces in stems - float and O2 can diffuse everywhere
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where are hydrophytes found?
in wet areas
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where are xerophytes found?
in dry areas
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what are the adaptive features of xerophytes?
leaves are tough with thick, waxy cuticle - reduce transpiration AND leaves roll up (stomata inside) - traps moist air, reduce water potential gradient = less transpiration AND roots spread wide - anchoring plant in loose sand
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example of a hydrophyte?
water lily
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example of a xerophyte?
marram grass
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what happens during natural selection?
variation within populations, production of many offspring, competition for resources (struggle for survival), reproduction by individuals that are better adapted to the environment than others = passing on of their alleles to the next generation
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what is evolution?
the change in adaptive features of a population over time as the result of natural selection
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what is the process of adaption?
the process, resulting from natural selection, by which populations become more suited to their environment over many generations
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what is an example of evolution by natural selection?
development of strains of antibiotic resistant bacteria
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how does bacteria become resistant to antibiotics?
Some bacteria have antibiotic resistant alleles, those without allele = don’t survive, with allele = survive and reproduce, next generation will almost all have this resistance allele
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what do both selective breeding and natural selection rely on?
genetic variation within a population
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what is the difference between natural selection and selective breeding?
NS - individuals with best adapted variation to environment = survive/ reproduce BUT SB - individuals with variations that humans want = survive/ reproduce
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what does selective breeding involve?
selection by humans of individuals with desirable features / crossing these individuals to produce the next generation / selection of offspring showing the desirable features
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how is artificial selection by selective breeding done? useful?
over many generations, it can improve crop plants and domesticate animals
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what are bacteria useful for? why?
in biotechnology and genetic engineering. because they reproduce rapidly / have ability to make complex molecules / lack of ethical concerns over manipulation and growth / genetic code shared with all organisms / presence of plasmids
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what is the role of yeast in anaerobic respiration?
yeast respires to produce ethanol and carbon dioxide
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why is ethanol a good product of anaerobic respiration of yeast?
it s used as a biofuel - made by living organisms
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why is yeast used in bread making?
CO2 is produced which makes bread rise, once cooked all ethanol is bread is destroyed
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what is pectinase?
an enzyme that breaks down pectin - holds plant cells together
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what does adding pectinase to fruits do?
easier to crush and extract juice, makes juice look less cloudy
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what do biological washing powders contain?
enzymes - protease, lipase, amylase
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what is lactase?
an enzyme that breaks down the disaccharide lactose, found in milk
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what is the equation for breaking down of lactose?
lactose = glucose + galactose
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what can adding lactase to milk do?
it breaks down lactose producing lactose-free milk
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what is penicillin used for?
treating many bacterial infections
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what is penicillin made from?
fungus called Penicillium
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how is penicillin made?
fungus grown in a fermenter. nutrients (amino acids, sugar) and oxygen are supplied, contents are collected and penicillin is extracted and purified
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what is genetic engineering?
changing the genetic material of an organism by removing, changing or inserting individual genes
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what are examples of genetic engineering?
put human genes into bacteria to produce human insulin / put genes into crop plants to confer resistance to herbicides or to insect pests / put genes into crop plants to provide additional vitamins
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explain genetic engineering using bacterial production of a human protein?
Isolate DNA with restriction enzymes = forms sticky ends / cut bacterial plasmid DNA with restriction enzymes, forms sticky ends / put human DNA into bacterial plasmid DNA using DNA ligase = forms recombinant plasmid, put into bacteria / reproduce
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what are advantages of genetically modifying crops, such as soya, maize and rice?
extra vit A = more nutritious (no night blindness) AND make own toxins to kill insects pests = reduce costs to farmer AND crops are resistant to herbicides = farms can weed crops = increase yields
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what are disadvantages of genetically modifying crops, such as soya, maize and rice?
more expenive than normal seeds AND very technical process requires skilled people + high-quality facilities AND worried about eating = ill
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Card 2

Front

what is a chromosome?

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a threadlike structure of DNA, carrying genetic information in the form of genes

Card 3

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what is a gene?

Back

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Card 4

Front

how do humans inherit their gender?

Back

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Card 5

Front

what is the chance of being a boy or a girl?

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