The origins of genetic variation

Question 1

Genotype

Answer 1

All the genes and alleles an organism has

Question 2

Phenotype

Answer 2

Alleles that are expressed as a characteristic

Question 3

Allele

Answer 3

A version of the same gene

Question 4

Locus

Answer 4

Position of a gene

Question 5

Homozygous

Answer 5

2 is the same alleles

Question 6

Heterozygous

Answer 6

2 different alleles

Question 7

Dominant

Answer 7

Alleles that are expressed

Question 8

Recessive

Answer 8

Only expressed with 2 alleles present and without dominant present

Question 9

Co dominant

Answer 9

2 equally dominant alleles

Question 10

Multiple alleles

Answer 10

More than 2 alleles for the same trait

Question 11

Gene

Answer 11

A sequence of bases on a DNA molecule coding for a sequence of amino acids on a polypeptide chain

Question 12

Monohybrid inheritance

Answer 12

Study of the inheritance of one characteristic

Question 13

Monohybrid inheritance: phenotypic ratio of F2 generation

Answer 13

3:1 dominant: recessive

Question 14

Monohybrid with codominant alleles phenotypic ratio

Answer 14

1:2:1 with the 2 being both traits expressed

Question 15

Law of segregation

Answer 15

Characteristics of a diploid organism are determined by pairs of alleles only one of which is transferred to a gamete

Question 16

What is a test cross used for

Answer 16

Used to determine whether an organism showing the dominant characteristic is homozygous or heterozygous

Question 17

How to perform a test cross

Answer 17

Cross with a homozygous recessive. If offspring show the recessive trait the parent must be heterozygous

Question 18

Cystic fibrosis

Answer 18

Recessive allele of a gene on chromosome 7. Normally codes for membrane protein production- CF thick mucus is produced in lungs and pancreas

Question 19

Huntington’s disease- why does this dominant allele survive in the population?

Answer 19

Delayed penetrance- symptoms don’t start until later in lire when person has most likely reproduced and passed on allele already

Question 20

Male and female heterosomes

Answer 20

Female- XX male- XY

Question 21

Genes located on heterosomes are

Answer 21

Sex linked

Question 22

Y linked diseases

Answer 22

Rare as there is little room on the chromosome

Question 23

Can males be carriers of X linked disease?

Answer 23

No but they can have the condition

Question 24

Why is X linkage more common?

Answer 24

X chromosome is larger
Part of it doesn’t have a homologous section of the Y chromosome so only one allele of a gene is present- it is always expressed

Question 25

Dihybrid inheritance

Answer 25

2 characteristics that are controlled by different genes at different loci

Question 26

Dihybrid F2 generation phenotypic ratio

Answer 26

9:3:3:1

Question 27

Genes and the environment

Answer 27

Genotype and environment result in phenotype

Question 28

Polygenic inheritance

Answer 28

Phenotype trait controlled by more than one gene

Question 29

Linkage

Answer 29

Genes that are closely located on the same chromosome tend to be inherited together unless crossing over separates them

Question 30

In crosses where linkage is happening a large proportion of the offspring are..

Answer 30

Of the parental genotype Could expect a 3:1 ratio if genes are linked in dihybrid because they are inherited as one

Question 31

Types of selection

Answer 31

Distriptive Stabilising Directional

Question 32

What is a gene pool

Answer 32

Total information from all the genes and alleles of the breeding individuals in a population at a particular time

Question 33

What is happening if there is a constant change in allele frequency in a population

Answer 33

The population is evolving because the proportion of organisms in the population carrying a particular allele

Question 34

Allele frequency

Answer 34

Number of different alleles for the same trait

Question 35

Genetic drift

Answer 35

Random changes in allele frequency

Question 36

Effect of genetic drift in a large population

Answer 36

Little effect and allele frequency remains stable

Question 37

Effect of genetic drift on a small population

Answer 37

Large impact

Question 38

Population bottlenecks

Answer 38

Occurs when a genetically diverse population is drastically reduced by a non selective event eg volcano Total genetic diversity of survivors likely to be much lower- this will be maintained even as population re establishes

Question 39

The founder effect

Answer 39

When a new population is founded from a subset of the original population eg migration of an island

Question 40

What does the hardy Weinberg assume

Answer 40

The population is large Has random mating Is experiencing no selection Has no mutation emigration or immigration

Question 41

What are the equations for hardy Weinberg

Answer 41

``` p+q = 1 p2+2pq+q2= 1 ```