B2.7 Cell Division and Inheritance

Question 1

How does sexual reproduction give rise to variation?

Answer 1

Reproduction without the need for fertilisation.

Question 2

How are inherited characteristics controlled?

Answer 2

Some controlled by a single gene.

Others controlled by a number of genes.

Question 3

What is an allele?

Answer 3

A different form of a gene.

Question 4

What is a dominant allele?

Answer 4

An allele which controls a characteristic when it is present on only one of the chromosomes in the pair.

Question 5

What is a recessive allele?

Answer 5

An allele which controls the development of characteristics only if the dominant allele is not present.

Question 6

Which molecule are chromosomes made from and what is its structure like?

Answer 6

DNA.

Question 7

What is a gene?

Answer 7

A small section of DNA.

Question 8

What does a gene contain?

Answer 8

The genetic code for a particular sequence of amino acids which makes a specific protein.

Question 9

What does DNA fingerprinting tell us?

Answer 9

Each person had a unique DNA which can be used to identify individuals.

Question 10

What are the female sex chromosomes?

Answer 10

XX.

Question 11

What are the male sex chromosomes?

Answer 11

XY.

Question 12

What is a mono-hybrid cross?

Answer 12

A cross(joining of gametes) between organisms which looks at only one allele at a time.

Question 13

What does homozygous and heterozygous mean?

Answer 13

Homozygous means both alleles which code for a particular protein are the same - bb or BB.
Heteroxygous means alleles are different - Bb.

Question 14

What does genotype mean?

Answer 14

A description of the alleles present.

Question 15

What does phenotype mean?

Answer 15

A description of the observed characteristics eg brown hair.

Question 16

What are genetic disorders?

Answer 16

Disorders which are inherited due to mutations in genes.

Question 17

What is ‘polydactlyly’ ?

Answer 17

When a person is born with extra digits.

Fingers or toes.

Question 18

How is polydactlyly inherited?

Answer 18

It is caused by a dominant allele and can be passed on by only one parent who has the disorder.

Question 19

What is cystic fibrosis?

Answer 19

A disorder of cell membrane which makes patients produce more mucus than normal.
Particularly in the lungs.

Question 20

How is cystic fibrosis inherited?

Answer 20

It is a recessive disorder so both parents must be carriers of the cystic fibrosis allele.

Question 21

What does a ‘carrier’ mean?

Answer 21

Someone who has the allele for a disorder but does not have the disorder themselves.
Carriers can only be present in inherited disorders which are recessive.

Question 22

How can you carry out screening for these disorders?

Answer 22

You can screen embryos for the allele of genetic disorders.

Question 23

What is a genetic pedigree?

Answer 23

A diagram that shows who in a family have a genetic disorder are carriers and are normal.

Question 24

What ideas did Mendal propose and why was this discovery not recognised until after his death?

Answer 24

They did not take him seriously and knew nothing about genes.

Question 25

Which organism did Mendal carry out most of his research on?

Answer 25

He looked at pea plants.