Genetics

Question 1

What is a gene

Answer 1

a sequence of bases on a DNA molecule that codes for a protein (polypeptide) which results in a characteristic

Question 2

What is an allele

Answer 2

Different versions of the same gene

Question 3

How many alleles doe humans typically carry per gene

Answer 3

2, one from each parent

Question 4

Why is the order of bases in each allele slightly different

Answer 4

because each allele codes for different versions of the same characteristic

Question 5

Humans are

Answer 5

Diploid organisms

Question 6

What does a diploid organism mean

Answer 6

we have two copies of each chromosome, one from each parent

Question 7

What is the locus

Answer 7

The position of the allele on a gene

Question 8

What is the genotype of an organism

Answer 8

Its genetic constitution/ the different alleles an organism has

Question 9

What is the phenotype

Answer 9

the expression of genetic constitution and it’s interaction with the environment

Question 10

What is a dominant allele

Answer 10

An allele that is always expressed in the phenotype

Question 11

What are recessive alleles

Answer 11

They’re only expressed if two copies are present

Question 12

What are codominant alleles

Answer 12

When both alleles are expressed in the phenotype because neither one is recessive

Question 13

What does homozygous mean

Answer 13

When an organism carries two copies of the same allele

Question 14

What does heterozygous mean

Answer 14

When an organism carries two different alleles for a gene

Question 15

What are gametes

Answer 15

sex cells

Question 16

How many alleles per gene do gametes contain

Answer 16

only one allele

Question 17

What are haploid cells

Answer 17

A cell that contains a single set of chromosomes

Question 18

What are diploid cells

Answer 18

A cell that contains two complete sets of chromosomes

Question 19

What is monohybrid inheritance

Answer 19

The inheritance of a characteristic controlled by a single gene

Question 20

What is the phenotypic ratio

Answer 20

The ratio of different phenotypes in the offspring

Question 21

What is the usual ratio between two heterozygous parents

Answer 21

3:1, dominant : recessive

Question 22

One example of codominance

Answer 22

sickle-cell anaemia

Question 23

What is the expected ratio with two heterozygous parents involving codominant alleles

Answer 23

1:2:1

Question 24

What is dihybrid inheritance

Answer 24

The inheritance of two characteristics which are controlled by different genes. Each of the two genes will have different alleles

Question 25

What is the expected ratio with a dihybrid cross with two heterozygous parents

Answer 25

9:3:3:1

Question 26

What does it mean if some characteristics are sex linked

Answer 26

The alleles that code for them are located on a sex-chromosome

Question 27

What is the difference between X and Y chromosomes

Answer 27

Y is much smaller and carries fewer genes

Question 28

Why do men often only have one allele for sex-linked genes

Answer 28

As males only have one X chromosomes

Question 29

Why are males more likely than females to show recessive phenotypes for genes that are sex-linked

Answer 29

As they only have one copy they express the characteristic of this allele even if it's recessive

Question 30

What are X-linked disorders

Answer 30

When faulty alleles for genetic disorders are carried on the X-chromosome

Question 31

What are X-linked genes

Answer 31

Genes on the sex chromosomes which are carried on the X-chromosome

Question 32

What does autosome stand for

Answer 32

Any chromosome that isn't a sex chromosome

Question 33

What are autosomal genes

Answer 33

The genes located on the autosome

Question 34

Why are genes on the autosome said to be linked

Answer 34

Because they'll stay together during the independent segregation of chromosomes in meiosis I and their alleles will pass on to the offspring together

Question 35

What prevents autosomal linkage

Answer 35

crossing over

Question 36

The closer together two genes are on the autosome the more closely they are said to be

Answer 36

linked because crossing over is less likely to occur

Question 37

What is epistasis

Answer 37

when two genes on different chromosomes affect the same feature. They interact to form the phenotype. One gene masks (blocks) the expression of the alleles of other genes.

Question 38

If the epistatic allele is recessive then

Answer 38

Two copies of it will mask the expression of the other gene

Question 39

If you cross a homozygous recessive parent with a homozygous dominant parent you will produce what phenotypic ratio

Answer 39

9:3:4

Question 40

If the epistatic allele is dominant then having at least one copy of it will

Answer 40

Mask the expression of the other gene

Question 41

Crossing a homozygous recessive parent with a homozygous dominant will produce what phenotypic ratio

Answer 41

12:3:1

Question 42

What is the observed result

Answer 42

The actual result of the experiment

Question 43

What is the expected result

Answer 43

The result predicted by the theory

Question 44

What is the critical value

Answer 44

the value of chi squared that corresponds to a 0.05 (5%) level of probability that the difference between our observed and expected results is due to chance.