Inheritance

Question 1

What is a gene?

Answer 1

A gene is a section of a molecule of DNA and codes for a specific protein

Question 2

What does a DNA molecule look like?

Answer 2

A DNA molecule is two strand coiled to form a double helix, being linked by a series of base pairs

Question 3

What are the complimentary base pairs?

Answer 3

• adenine and thymine

- cytosine and guanine

Question 4

What is a dominant allele?

Answer 4

An allele which is always expressed

Question 5

What is a recessive allele?

Answer 5

An allele only expressed if both alleles are recessive (homozygous)

Question 6

What does homozygous mean?

Answer 6

Having two of the same alleles

Question 7

What does heterozygous mean?

Answer 7

Having two different alleles

Question 8

What is a phenotype?

Answer 8

The physical characteristics an organism has

Question 9

What is a genotype?

Answer 9

A set of alleles

Question 10

What is codominance?

Answer 10

It’s what happens when both alleles are expressed in the same phenotype

Question 11

How do you read a family pedigree?

Answer 11

The squares are male
The circles are female
If the shape is coloured in, that family member is affected by the genetic trait

Question 12

Why is a family pedigree useful?

Answer 12

It shows the pattern of inheritance of a genetic trait

Question 13

What is the sex of a person controlled by?

Answer 13

A pair of chromosome:
XX is female
XY is male

Question 14

Why are heterozygous individuals often called carriers?

Answer 14

Because they carry the allele for the recessive characteristic so do not show the trait, but can pass it on to their offspring

Question 15

When does mitosis occur?

Answer 15

In growth, repaid, cloning and asexual reproduction

Question 16

What does the division of a diploid cell by mitosis produce?

Answer 16

Two daughter cells which contain identical sets of chromosomes

Question 17

What does the division of a cell by meiosis produce?

Answer 17

Four daughter cells, each with half the number of chromosomes - resulting in the formation of genetically different haploid cells

Question 18

What produces genetic variation in offspring?

Answer 18

Random fertilisation

Question 19

How many chromosomes are there in diploid and haploid human cells?

Answer 19

Haploid: 23
Diploid: 46

Question 20

What is a mutation?

Answer 20

A mutation is a rare, random change in a gene that can be inherited. It can be neutral, beneficial or harmful.

Question 21

Describe the process of evolution by means of natural selection

Answer 21

• a mutation occurs
• if the mutation is beneficial, the animal will survive longer and reproduce more
• some offspring will inherit the mutation
• the offspring will have a better chance of survival, so they’ll live longer and reproduce more
• over long periods of time, the process is repeated and gradually the mutation becomes a common gene

Question 22

What happens if bacteria experience mutations?

Answer 22

Bacteria experience mutations which can mean they’re no longer affected by a certain antibiotic. If they evolve to become resistant to drugs, they are difficult to control

Question 23

How can the chances of mutation be increased?

Answer 23

• by exposure to ionising radiation (eg gamma rays and X-rays)
• by some chemical mutagens (eg chemicals in tobacco)

Question 24

What does the nucleus of a cell contain?

Answer 24

It contains chromosomes on which genes are located