Patterns of inheritance

Question 1

What is continuous variation

Answer 1

Individuals in a population vary within a range

Question 2

What is discontinuous variation

Answer 2

When there are two or more distinct categories

Question 3

Define allele

Answer 3

Different versions of genes

Question 4

How does meiosis make gametes with a unique assortment of alleles

Answer 4

Through crossing over and independent assortment of chromosomes

Question 5

What is variation in phenotype

Answer 5

Phenotypic variation

Question 6

What is polygenic characteristics and what type of variation are they normally

Answer 6

A characteristic influenced by two or more genes typically continuous variation

Question 7

What is monogenic characteristics and what type of variation are they normally

Answer 7

Characteristics controlled by only one gene typically monogenic

Question 8

Define gene

Answer 8

A sequence of bases on a DNA molecule that codes for a protein resulting in a characteristic

Question 9

Define genotype

Answer 9

The alleles and organism has e.g BB

Question 10

Define phenotype

Answer 10

The characteristics the alleles produce e.g brown eyes

Question 11

Define dominant

Answer 11

An allele whose characteristic only appears in the phenotype even when there is only one copy shown by a capital letter

Question 12

Define recessive

Answer 12

An allele whose characteristic only appears on the phenotype if two copies are present shown by lower case letters

Question 13

Define codominant and an example

Answer 13

Alleles that are both expressed in the phenotype - neither one is recessive. Such as sickle cell anaemia

Question 14

Define locus

Answer 14

The fixed position of a gene on a chromosome. Alleles of a gene are found at the same locus on each chromosome in a pair

Question 15

Define homozygote

Answer 15

An organism that carries two copies of the same allele

Question 16

Define heterozygote

Answer 16

An organism that carries two different alleles

Question 17

Define carrier

Answer 17

A person carrying an allele which is not expressed in the phenotype but that can be passed on to offspring

Question 18

What is monogenic inheritance

Answer 18

Inheritance of a characteristic controlled by a single gene

Question 19

What does monogenic crosses show

Answer 19

The likelihood of different alleles of that gene being inherited by offspring of particular parents

Question 20

How to draw out a monogenic cross diagram steps

Answer 20

1) Parents genotypes
2) Gametes alleles
3) Possible genotypes of F1 offspring
4) Gametes alleles
5) Possible genotypes of F2 offspring
6) Phenotypes
7) Ratio in F2 offspring

Question 21

What is dihybrid inheritance

Answer 21

The inheritance of two characteristics which are controlled by different genes

Question 22

Expected phenotypic ratio of monogenic cross for F2 generation

Answer 22

3:1

Question 23

Expected dihybrid ratio of monogenic cross for F2 generation

Answer 23

9:3:3:1

Question 24

Expected phenotypic ratio of codominant cross for F2 generation

Answer 24

1:2:1

Question 25

Why wont the expected ratios from different types of genetic crosses occur

Answer 25

Sex linkage, autosomal linkage or epistasis

Question 26

What is a sex linked characteristic

Answer 26

When the allele that codes for the characteristic is located on a sex chromosome (X/Y)

Question 27

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

Answer 27

They only have one X chromosome and only one allele for sex-linked genes. As they only have one copy they express the characteristic of this allele even if it is recessive. Such as colour blindness

Question 28

What is an autosome

Answer 28

Any chromosome that is not a sex chromosome

Question 29

What are autosomal genes

Answer 29

Genes located on autosomes

Question 30

Genes on the same autosome are... and why

Answer 30

Linked - they will stay together during independent assortment of chromosomes in meiosis I and their alleles will be passed on to the offspring together unless crossing over splits them up before.

Question 31

What does the closer the genes on an autosome mean

Answer 31

They are more closely linked as crossing over is less likely to split them up

Question 32

Why won't you see the expected phenotypic ratio of a cross that are autosomally linked

Answer 32

The two autosomally linked alleles are inherited together so there is a higher proportion of the offspring that will have their parents genotype and phenotype.

Question 33

What is epistasis

Answer 33

When the allele of one gene masks the expression of the alleles of other genes such as hair colour and baldness

Question 34

A dihybrid cross produces the phenotypic ratio of 9:3:4 in the F2 generation. What does this indicate about the genes involved

Answer 34

It involves a recessive epistatic allele

Question 35

A dihybrid cross produces the phenotypic ratio of 12:3:1 in the F2 generation. What does this indicate about the genes involved

Answer 35

Crossing a homozygous recessive with a homozygoua dominant

Question 36

What can the chi squared test be used for

Answer 36

To see if the results of an experiment support a theory

Question 37

What is a null hypothesis

Answer 37

There is no significant difference between the observed and expected results - results are due to chance

Question 38

How to work out the Chi-Squared Value

Answer 38

1) Work out the expected value for each phenotype 2) Record the actual number of offspring recorded 3) Subtract the expected result from the observed result 4) Square this number and divide by the expected result 5) Add all the numbers together to get the sum X^2 = (O-E)^2 / E

Question 39

What is the critical value

Answer 39

The value of X^2 that corresponds to a 0.05 (5%) level of probability that the difference between the observed and expected results is due to chance

Question 40

When can the null hypothesis be rejected

Answer 40

If the X^2 value is larger or equal to the critical value then there is a significant difference

Question 41

When can the null hypothesis be accepted

Answer 41

If the X^2 value is smaller than the critical value and then there is no significant difference

Question 42

What are degrees of freedom

Answer 42

The number of phenotypes/classes