inheritance 💸

Question 1

define genes

Answer 1

genes are a unit of inheritance with a specific sequence of nucleotides, as part of a DNA molecule that codes for a polypeptide

Question 2

define allele

Answer 2

allele is one of two or more different forms of a gene

Question 3

define a dominant allele

Answer 3

allele that can always be expressed in the phenotype, when it occurs in the homozygous or heterozygous condition

Question 4

define a recessive allele

Answer 4

allele that is only expressed in the phenotype when it occurs in the homozygous condition

Question 5

define homozygous

Answer 5

organism having two identical alleles of a particuler gene

Question 6

define heterozygous

Answer 6

organism having two different alleles of a particular gene

Question 7

define codominance

Answer 7

when both alleles have an equal effect on the phenotype of the offspring (equally dominant)

Question 8

define genotype

Answer 8

the genetic makeup of an organism

Question 9

define phenotype

Answer 9

an observable trait or physical appearance of an organism

Question 10

order of genetic diagram drawing

Answer 10

1) key: let B represent dominant allele for.. , let b represent recessive allele for…
2) parental phenotype: A x B
3) parental genotype: A x B
4) gametes: O O O O
5) punnet square
6) offspring genotype: BB Bb Bb bb
7) offspring phenotype: A B
8) offspring phenotypic ratio: 3:1

Question 11

why do the observed ratios differ from the expected ratios?

Answer 11

ratios are inaccurate for small sample size

Question 12

describe a test cross

Answer 12

an individual with unknown genotype is crossed with one who is homozygous recessive, used to test whether individual is homozygous or heterozygous in the gene
- if all offspring show dominant, individual is homozygous dominant
- if offspring is mixed dominant recessive, individual is heterozygous

Question 13

why is a homozygous individual used in a test cross

Answer 13

all of their gametes must contain the recessive allele of the gene, which will have no effect on the phenotype of the offspring

Question 14

define multiple alleles

Answer 14

a gene that exists in more than two alleles

Question 15

define mutation

Answer 15

mutation is a spontaneous or sudden change in the DNA sequence of genes, or chromosome structure or number.

Question 16

what mutagens can increase the rate of mutation

Answer 16

1) radiation (ultraviolet, x-ray, gamma ray)
2) chemical mutagens (tar)

Question 17

define variations and its causes

Answer 17

variations are the difference in traits between individuals of the same species, caused by genetic or environmental factors

Question 18

compare continuous and discontinuous variation

Answer 18

phenotype: range of phenotypes vs range of phenotypes
affected by environment?: greatly vs unaffected
controlled by: many genes vs one of a few genes
data: quantitative, continuous range vs qualitative, discrete groups

Question 19

describe the process of natural selection

Answer 19

1) spontaneous mutation leads to variation within the species
2) there is competition for finite resources (food, water, space etc)
3) state the aadvantageous characteristic
4) …which is best adapted to the environment, allowing them to survive till maturity.
5) they will have a higher chance of reproducing and passing down these desirable traits to the offspring

Question 20

describe the process of artificial selection / selective breeding

Answer 20

1) the individuals showing the desired quality are selected (state the characteristics)
2) the individuals are used as breeding stoock
3) only the offspring showing the desired quality to the greatest extent are selected and used for breeding