Inheritance

Question 1

What is a genotype?

Answer 1

Genetic make up of an organism.

ALL the alleles that an organism has.

Question 2

What is an allele?

Answer 2

Different versions of a gene found at the same locus on a chromosome.

Question 3

What is a gene?

Answer 3

Short section of DNA that codes for a single polypeptide

Question 4

What is a phenotype?

Answer 4

Observable or biochemical characteristics of an organism.

Expression of the genotype and its interaction with the environment.

Question 5

What is a homologous chromosomes

Answer 5

A pair of chromosomes matched in shape and size, which contain the same genes.
Formed when haploid gametes fuse to make zygote at fertilisation

Question 6

Locus

Answer 6

Position of a gene on a chromosome

Question 7

Homozygous

Answer 7

Two alleles at a gene locus are the same

Question 8

Heterozygous

Answer 8

Two alleles at a gene locus are different

Question 9

Dominant allele

Answer 9

The allele of the heterozygote that is expressed in the phenotype

Question 10

Recessive allele

Answer 10

The allele that is only expressed when homozygous. It is not expressed when a dominant allele is present.

Question 11

A dominant allele is …

Answer 11

Where both alleles are expressed in the phenotype

Question 12

What are multiple alleles?

Answer 12

There are more than two alleles for a particular gene

Question 13

In a diploid human cell how many chromosome pairs are there?

Answer 13

23

Question 14

In meiosis, what happens to the diploid number?

Answer 14

It becomes haploid.

It halves

Question 15

Characteristics are determined by your allele combinations. How many alleles for each characteristic are present in a gamete?

Answer 15

1

Question 16

Pure breeding plants are said to be …

Answer 16

Homozygous

Question 17

What is the difference between monohybrid inheritance and dihybrid inheritance?

Answer 17

Monohybrid - inheritance of a SINGLE gene

Dihybrid - inheritance of TWO genes (that are located on different chromosomes)

Question 18

Give an example of a characteristic that involves multiple allelles

Answer 18

Blood groups

Question 19

Identify the chromosomes that determine sex

Answer 19

X and Y

In most organisms XX = female and XY = male

Question 20

When might you use a Chi squared test?

Answer 20

Sample size is large (20+)
Data falls int categories
Compare experimental observations with theoretical/expected ones.

Question 21

When performing a statistical test what must you always state before you carry out the test?

Answer 21

Null hypothesis

There is no significant difference between …. and …

Question 22

What are autosomes?

Answer 22

The chromosomes that are not the sex chromosomes. In humans there are 22 pairs of autosomes.

Question 23

What is meant by autosomal linkage?

Answer 23

Two (or more) genes are carried on the SAME chromosome

Question 24

For autosomal linkage what do we have to assume?

Answer 24

There is no crossing over

Genes remain together during meiosis

Question 25

What is epistasis?

Answer 25

The allele of one gene affects or masks the expression of another allele in the phenotype

Question 26

What phenotypic ratio would you expect for a monohydrid cross between two heterozygous individuals?

Answer 26

3:1 | 3 dominant : 1 recessive

Question 27

What phenotypic ratio would you expect for a dihybrid cross between two heterozygous individuals?

Answer 27

9:3:3:1

Question 28

A carrier is ....

Answer 28

A person in possession of an allele that is not expressed in the phenotype

Question 29

What phenotypic ratio would you expect for codominant cross between 2 heterozygotes?

Answer 29

1:2:1

Question 30

Sometimes you do not get expected phenotypic ratios because ...

Answer 30

Small sample size Autosomal linkage Epistasis

Question 31

Name a sex linked condition

Answer 31

Haemophilia | Colour blindness

Question 32

A characteristic is said to be sex linked when ...

Answer 32

Its is carried on the sex chromosomes

Question 33

How can you tell from a pedigree chart if a condition is sex linked.

Answer 33

Males will only be affected

Question 34

Why are males more likely to express recessive traits of sex linked conditions?

Answer 34

Only have 1 copy of X chromosome | No second allele to mask a recessive one

Question 35

How are X and Y chromosomes different?

Answer 35

X is bigger/contains more genes | Y is smaller/contains fewer genes

Question 36

When might genes that are present on the same chromosome NOT be inherited together?

Answer 36

Crossing over in meiosis I

Question 37

The closer together 2 genes are the more closely linked they are - why?

Answer 37

Crossing over is less likely to split them up

Question 38

If two genes are said to be linked what does this mean?

Answer 38

They are on the same chromosome

Question 39

What is meant by codominant alleles?

Answer 39

Two dominant allleles that both contribute to the phenotype, by showing a blend of both characteristics or the characteristics appearing together.

Question 40

A woman has the blood group O. Give her genotype.

Answer 40

XX Io Io

Question 41

A male has blood group AB. Give his genotype

Answer 41

XY IA IB