alleles and inheritance

Question 1

state –> alleles are different versions of the same gene

Question 2

what determines what characteristics we develop

Answer 2

the genes you develop control what characteristics you develop

Question 3

state –> some charactaristics are controlled by a single gene. however most charecacteristics are controlled by several genes interacting

Question 4

how many copies of each gene do we have

Answer 4

two copies of each gene, one from each parent

Question 5

state –> the version of the characteristic that appears is caused by the dominant allele. The other allele is said to be recessive. The characteristic is caused by recessive allele only appears if both alleles are recessive

Question 6

codominant alleles

Answer 6

some characteristics are caused by codominant alleles. neither

Question 7

genetic diagrams letters are used to represent genes

Answer 7

• in diagrams diagrams, letters are used to represent genes. dominant alleles are always shown with a capital letter. recessive alleles with a small letter
• if you are homozygous for a trait you have two alleles the same for that particular gene
• if you are heterozygous for a trait you have two different alleles for that particular gene
• your genotype is the alleles that you have. your phenotype is the characteristics the alleles produce.

Question 8

state –> there are 23 matched pairs of chromosomes in every human body cell.

Question 9

what is the 23rd pair labelled as

Answer 9

XX or XY

Question 10

what does XX or XY tell you

Answer 10

whether you turn out female or male

Question 11

what do males have

Answer 11

an X and Y chromosome. (the Y chromosome causes male characteristics

Question 12

what do females have

Answer 12

females have two X chromosomes. XX
The XX combination causes female characteristics

Question 13

why are animals all bound to be slightly different

Answer 13

because their genes are slightly different

Question 14

what is most variation caused by

Answer 14

a mixture of genetic and environmental factors

Question 15

how can the environment have a large effect on human growth before someone is born

Answer 15

a baby’s weight at brith can be affected by the mother’s diet. and another having a poor diet whilst you are growing up can stunt your growth

Question 16

state –> environmental variation in plants is much greater

Question 17

what are plants strongly affected by

Answer 17

• sunlight
• moisture level
• temperature
• the mineral content of soil

Question 18

theory of evolution

Answer 18

life began as simple organisms from which more complex organisms evolved ( rather than just popping into existence)

Question 19

how long does the whole process of evolution take

Answer 19

it takes place gradually over millions of years

Question 19

what does natural selection mean

Answer 19

the ‘ survival of the fittest’

Question 19

darwins theory

Answer 19

• darwin knew that organisms in a species show variation in their characteristics
• darwin also knew that the resources that organisms need to survive are limited and individuals have to compete for these resources to survive
• darwin concluded that the organisms with the most suitable characteristics for the environment would be more successful competitors and so would have a better chance of survival 0 this is known as survival of the fittest
• the successful organisms will then have an increased chance of breeding and passed on their genes
• this means that a greater proportion of individuals in the next generation will have the better alleles and so the characteristics, that help survival
• over many generations, the characteristic that increases survival becomes more common in the population, making the species become better and better able to survive. the ‘best’ features are naturally selected and the species becomes more and more adapted to its environment

Question 20

who came up with the theory of evolution by natural selection

Answer 20

charles darwin

Question 20

state –> the best genes for a particular environment tend to survive

Question 21

the individuals who are less suited to an environment…

Answer 21

are less likely to survive than those that are better suited and so have less chance to pass their alleles on

Question 22

what are variations caused by

Answer 22

by the environment itself. variations in a species can have either environmental or genetic causes, but only the genetic ones are passed on to the next generation and influence the evolution of the species.

Question 23

state --> mutations are changes to the genetic code

Question 24

what is a mutation

Answer 24

is a rare, random change in an organism's DNA that can be inherited

Question 25

what do mutations do

Answer 25

change the sequence of the DNA bases in a gene which produces a genetic variant. As the sequence of DNA bases codes for the sequence of amino acids that make up a protein, mutations to a gene sometimes lead to changes in the protein that it codes for

Question 26

what is a genetic variant

Answer 26

different form of the gene

Question 27

state --> enzymes are proteins which need an active site with a very specific shape to be able to work properly. a mutation in the gene that codes for an enzyme could lead to a change in the shape of an enzyme's active site - altering its function. a mutation could also stop the production of the enzyme altogether

Question 28

what can mutations lead to

Answer 28

a different phenotype, increasing variation

Question 29

when can mutations happen

Answer 29

they can happen spontaneously - when a chromosome doesnt quite copy itself properly

Question 30

the chance of mutation is increased by exposing yourself to:

Answer 30

ionising radiation eg: X-rays, gamma rays or ultraviolet rays chemicals called mutagens eg: chemicals in tobacco

Question 31

no effect, small effect, significant effect - mutations

Answer 31

- most mutations have no effect. if mutation occurs in unimportant region of the DNA or if mutated codon still codes for same amino acid, the protein's structure and function will be unaffected. A mutation will also have no effect if it occurs in a recessive allele - some mutations have a small effect on the phenotype. This happens when the change in amino acid only has a slight effect on the protein's structure and function - so the individual's characteristics are only altered very slightly - very rarely, a mutation will have a significant effect on phenotype. for example it might result in a very different protein which can no longer carry out its function. These mutations can be harmful ( such as those which lead to cancer ) or beneficial (giving a survival advantage eg: antibiotic resistance in bacteria)

Question 32

how can bacteria evolve and become antibiotic resistant

Answer 32

- bacteria can sometimes develop random mutations in their DNA. These can lead to changes in a bacterium's characteristics. Sometimes, they mean that a bacterium is less effected by a particular antibiotic. - for the bacterium this ability to resist antibiotics is a big advantage. its better able to survive, eve in a host who is being treated to get rid of the infection, so it lives for longer and reproduces many more times - this leads to the alleles for resistance being passed on lots of offspring - its just natural selection. This is how it spreads and becomes more common in a population of bacteria over time. This is a problem for people who become infected with these bacteria, because they cannot easily get rid of them with antibiotics. Sometimes, drug companies can come up with a new antibiotic that is effective, but 'superbugs' that are resistant to most known antibiotics (eg: MRSA) are becoming more common)

Question 32

state --> bacteria can evolve and become antibiotic resistant