Genetics

not including much on Mendel or genetic diagrams or sex-linked genetic disorders 

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what is sexual reproduction?
its where genetic information from two organisms (a father and a mother) is combined.
fertilisation of female sex cell by male sex cell
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What is a gamete?
a sex cell
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how many chromosomes do they contain?
this makes them ........?
23
haploid
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what's a zygote?
a fertilised egg
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how does the zygote develop into an embryo?
it undergoes cell division by mitosis
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in humans where does meiosis take place?
reproductive organs only
(testes and ovaries)
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what's the product of mitosis?
two diploid cells genetically identical to each other and the parent cells
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what's the product of meiosis?
four haploid daughter cells that are genetically different
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when do gametes form a diploid cell?
when they fuse at fertilisation
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name 2 advantages and 1 disadvantage of asexual reproduction
advantages - can produce lots of offspring's very quickly, only one parent is needed
disadvantage - no genetic variation between offspring in the population
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why is producing lots of offspring quickly an advantage in asexual reproduction?
it can allow organisms to colonise a new area very rapidly
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why is only needing one parent an advantage in sexual reproduction?
organisms can reproduce when conditions are favourable without having to wait for a mate
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why is having no genetic variation between offspring a disadvantage in asexual reproduction?
if the environment changes and the conditions become unfavourable the whole population may be affected
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what's 1 advantage and 2 disadvantages of sexual reproduction?
advantage - genetic variation within a population
disadvantages - more time and energy than asexual reproduction, two parents needed
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why is genetic variation an advantage in sexual reproduction?
individuals have different characteristics so if environmental conditions change, more likely some individuals in the population have the characteristics to survive the change, over time this can lead to natural selection and evolution
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why is sexual reproduction taking more time and energy a disadvantage?
organisms produce fewer offspring in their lifetime
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how does sexual reproduction take more time and energy than asexual reproduction?
for sexual reproduction organisms have to find and attract a mate
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how can needing to parents be a disadvantage for a sexual reproduction?
if individuals are isolated it can be hard for them to find a mate
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how are DNA strands polymers?
there made up of repeating units called nucleotides
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what does each nucleotide consist of?
a sugar, a phosphate group and a base
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what forms a backbone for the DNA?
what's this backbone called?
the sugar and phosphate groups in the nucleotide
(called the sugar-phosphate backbone)
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what are the four bases that join to each sugar?
adenine, thymine, cytosine and guanine
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what shape is a DNA molecule?
a double helix
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what are the complementary base pairs?
adenine - thymine
cytosine - guanine
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how are complementary base pairs joined together?
weak hydrogen bonds
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what is a chromosome?
a long coiled up molecule of DNA
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where are chromosomes found?
in the nucleus of eukaryotic cells
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what is a gene?
a section of DNA on a chromosome that codes for a particular protein
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what makes ups an organism's genome?
all its DNA including the non-coding regions
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in the practical to extract DNA from fruit cells what is the detergent for?
it will break down the cell membrane
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what does the salt do?
makes the DNA stick together
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what does the ice-cold alcohol (ethanol) do?
How does it do this?
it's used to precipitate the DNA (make it visible)
DNA is not soluble in alcohol so it will come out of the solution.
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describe the practical to extract DNA from fruit cells
mash fruit, put in beaker containing solution of detergent and salt, mix, filter the mixture to get froth and insoluble bits of cell out, add ice-cold alcohol, DNA will appear as white participate, fish out with glass rod
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how does the DNA appear at the end of the practical?
as a stringy white participate (a solid)
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what controls the production of proteins in a cell?
DNA
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what are proteins made up of?
chains of molecules called amino acids
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each protein has its own particular number and order of ....... ?
amino acids
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the amino acid chains fold up to give each protein ........?
a different, specific shape
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what will this mean for the proteins?
they each have different functions
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what decides the order of amino acids in a protein?
the order of bases in a gene
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each amino acid is coded by a sequence of how many bases in the gene?
this is called?
three
a base triplet
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the amino acids are joined together to make what?
following what order?
proteins
following the order of bases in a gene
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what allows the gene to code for a particular protein?
the fact that each gene contains a different sequence of bases
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what is non-coding DNA?
DNA that doesn't code for any amino acids
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are some of the regions of DNA still used in protein synthesis?
yes
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what is a mutation?
a rare, random change to an organism's DNA base sequence that can be inherited
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what happens if a mutation occurs in a gene?
it produces a genetic variant - a different version of the gene
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what happens if a genetic variant codes for a different sequence of amino acids
it may change the shape of the final protein and so its activity
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what could this end up doing to an organism?
it may change their characteristic (phenotype)
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can mutations also happen in non-coding regions of DNA?
yes
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name the two stages that proteins are made in, in order
transcription
translation
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where are proteins made?
in the cell cytoplasm by subcellular structures called ribosomes
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why cant DNA move out of the nucleus?
it's too big
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how does the cell get the information from the DNA to the ribosome in the cytoplasm?
using a molecule called messenger RNA (mRNA)
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what is a similarity between DNA and mRNA?
they are both polymers of nucleotides
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how is mRNA different to DNA?
its shorter and only a single stand
it uses uracil instead of thymine as a base
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what's the name of the enzyme involved in joining RNA nucleotides to make mRNA?
RNA polymerase
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what's the first stage in transcription?
RNA polymerase binds to a region of non-coding DNA in front of a gene
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what's the second stage of transcription?
the two DNA strands unzip and the RNA polymerase moves along one strand of the DNA
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what's the third stage of transcription?
the RNA polymerase uses the coding DNA in the gene as a template to make the mRNA.
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base parings between DNA and RNA ensures what?
base parings between DNA and RNA ensures that the mRNA is complementary to the gene.
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what's the last stage of transcription?
once the mRNA molecule is made it moves out of the nucleus and joins with a ribosome
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what's the first stage of translation?
amino acids are bought to the ribosome by another RNA molecule called transfer RNA (tRNA)
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the order in which the amino acids are bought to the ribosomes matches what?
the order of base triplets in the mRNA
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what are base triplets in the mRNA also known as?
codons
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part of the tRNA's structure is called an anticodon - what's it complementary to?
the codon for the amino acid.
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what does the pairing of the codon and anticodon do?
it makes sure that the amino acids are bought to the ribosome in the correct order
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how are the amnio acids joined together?
by ribosomes
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what does this make?
a polypeptide (protein)
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before any transcription can happen, RNA polymerase has to bind to a what?
a region of non-coding DNA in front of a gene
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what happens if a mutation happens in this region of non-coding DNA?
it could affect the ability for RNA polymerase to bind to it, it could make it harder or easier.
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how well RNA polymerase can bind to this region of DNA will affect what?
how much mRNA is transcribed and therefore how much protein is produced and depending on the function of the protein the phenotype of the organism may be affected
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so genetic variants in non0coding DNA can still affect the phenotype of an organism even though they don't ..............?
code for proteins themselves
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what is one conclusion Mendel reached?
characteristics in plants are determined by 'hereditary units'
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what's a second conclusion he Mendel reached?
hereditary units are passed on to off-springs from both parents, one unit from each parent
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what's the third important conclusion Mendel reached?
hereditary units can be dominant or recessive - if an individual has both the dominant and the recessive unit for a characteristic the dominant characteristic will be expressed
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what do the genes you develop control?
different genes control what?
your characteristics
different genes control different characteristics
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all genes exist in different versions called what?
alleles
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how many versions of every gene do you have in your body?
2 - one on each chromosome in a pair
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what is meant by homozygous?
when both the alleles for a gene are the same in an organism
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what is meant by heterozygous?
when both the alleles for a gene are different in an organism
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alleles can be dominant or ..........?
recessive
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if an organism has one dominant allele and one recessive allele for a gene, which one would choose what characteristic is present?
the dominant allele
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for an organism to display a recessive characteristic what alleles must there be?
two recessive alleles
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what's your genotype?
the alleles for a certain characteristic that are found in an organism
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what is the inheritance of a single characteristic called?
monohybrid inheritance
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what are the male chromosomes?
xy
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what are the female chromosomes?
**
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how can a characteristic be sex-linked?
if the allele that codes for it is located on a sex chromosome (x or y)
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is they y or the x chromosome smaller?
the y chromosome is smaller
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because the y chromosome is smaller it carries fewer what?
genes
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so most genes on the sex chromosomes are only carried on the ........... ?
x chromosome
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why do men often only have one allele for sex-linked genes?
because they only have one x chromosome
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why can the characteristic of this allele be shown even if its recessive?
because they only have one allele
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what are sex-linked genetic disorders?
disorders caused by faulty alleles located on the sex chromosomes
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sometimes you can get multiple ......... for a single gene?
alleles
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what are the 4 potential blood groups humans can have?
O, A, B and AB
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how many different alleles does the gene for blood type have?
what are they?
3
IO, IA, IB
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what is meant by codominance?
when two alleles for a gene both affect the phenotype
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what two alleles for blood type are codominant?
what blood type will this genotype have?
IA and IB
they'll have the blood type AB
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which allele for blood type is recessive?
IO
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how do you get blood type O?
when there are two of the recessive alleles (IOIO)
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will organisms of the same species look slightly different?
yes
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what are these differences called
variation
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define genetic variation
differences between organisms caused by differences in the alleles they inherit from their parents or differences in genes caused by mutations, also called inherited variation
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define environmental variation
differences between organisms caused by environmental factors such as the amount of heat, light and damage by other organisms, these differences are called acquired characteristics
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why does there tend to be lots of genetic variation within a population of a species?
neutral mutations
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when mutations don't have nay affect they are........?
neutral
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what can happen if new combinations of alleles interact with each other?
they may produce new phenotypes
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what potential benifits for medicine has the human genome project had?
prediction and prevention of diseases, testing and treatment for inherited disorders, new and better medicines
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what are some drawbacks of the human genome project?
increased stress
gene-ism
discrimination by employers and insurance
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Other cards in this set

Card 2

Front

What is a gamete?

Back

a sex cell

Card 3

Front

how many chromosomes do they contain?
this makes them ........?

Back

Preview of the front of card 3

Card 4

Front

what's a zygote?

Back

Preview of the front of card 4

Card 5

Front

how does the zygote develop into an embryo?

Back

Preview of the front of card 5
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