7A genetics

Question 1

What is a gene

Answer 1

Sequence of bases on a dna molecule that codes for a polypeptide resulting in a characteristic

Question 2

What is an allele

Answer 2

One or more versions of the same gene

Question 3

What is a diploid cell

Answer 3

This is where there are 2 copies of each chromosome (one from each parent) which ends up in 2 alleles of each gene

Question 4

What is the name of the position where the allele is at a fixed point

Answer 4

Locus

Question 5

What is the genotype

Answer 5

Genetic constitution made up of the different alleles an organism has

Question 6

What is a phenotype

Answer 6

The expression of the genetic constitution and its interaction with the environment

Question 7

What is a dominant allele

Answer 7

Always expressed in phenotype even when theres just one copy

Question 8

What is a recessive allele

Answer 8

Characteristics only appear in the phenotype if two copies are present

Question 9

What is a codominant allele

Answer 9

Neither is recessive so both expressed

Question 10

What is the difference between homozygous and heterozygous

Answer 10

Homozygous is where it carries 2 copies of the same allele and heterozygous where it carries 2 different alleles for a gene

Question 11

What is a haploid cell?

Answer 11

Only one allele for each gene contained

Question 12

What is the importance of monohybrid inheritance and crosses

Answer 12

It is the inheritance of a characteristic controlled by one gene so the crosses show the different likelihoods of that gene being inherited by offspring of certain parents

Question 13

What is the phenotypic ratio for monohybrind crosses

Answer 13

3:1 (dominant to recessive)

Question 14

What is the expected phenotypic ratio for 2 heterozygous parents

Answer 14

1:2:1

Question 15

Importance of dihybrid inheritance and crosses

Answer 15

Inheritance of 2 characteristics controlled by different genes so the cross will show the likelihood of offspring inheriting certain combinations of the 2 characteristics from particular parents

Question 16

What is sex linkage

Answer 16

Alleles that code for them are located on a sex chromosome

Question 17

Why are males more likely to show recessive phenotypes for those that are sex linked

Answer 17

Males only have one copy of X chromosome so they express it

Question 18

What is the dominant epistatic phenotypic ratio?

Answer 18

crossing homozygous recessive with homozygous dominant will produce 12:3:1

dominant epistatic : recessive epistatic : dominant other : recessive both

Question 19

What causes x linked disorders

Answer 19

Where the faulty alleles are carried on the x chromosome

Question 20

When do you reject the null hypothesis?

Answer 20

When your x2 value is larger/equal to critical so there is a significant difference between O and E which could be due to something other than chance

Question 21

What is the chi squared formula?

Answer 21

chi squared = sum of (observed - expected)^2 / expected

Question 22

What is a critical value?

Answer 22

The value of x^2 that corresponds to a 0.05 level of probability that the difference between observed and expected is due to chance

Question 23

What is a null hypothesis?

Answer 23

This is where there is no significant difference between expected and observed results which sould be due to chance or a wrong theory

Question 24

How do you work out the degrees of freedom?

Answer 24

number of classes (phenotypes) - 1

Question 25

What is the chi squared test?

Answer 25

A statistical test that is used to see if the results of an experiment support a theory

Question 26

What is epistasis?

Answer 26

The allele of one gene masks the expression of another gene

Question 27

For recessive epistatic alleles what is the phenotypic ratio?

Answer 27

If you cross homozygous recessive with a homozygous dominant you produce a 9:3:4

dominant both: dominant epistatic: recessive other : recessive epistatic

Question 28

What is the expected ratio for 2 heterozygous parents in a dihybrid cross

Answer 28

9:3:3:1

Question 29

What is autosomal linkage

Answer 29

Genes located on the autosome that will stay together during independent segregation passing on their alleles to offspring together