B6 - Inheritance, Variation and Evolution

Question 1

What is DNA

Answer 1

The genetic material in the nucleus of a cell is composed of a
chemical and is a polymer made of two strands to form a double helix

Question 2

What is a gene

Answer 2

A gene is a small section of DNA on a chromosome

Question 3

What does each gene do

Answer 3

Each gene codes for a particular sequence of amino acids, to make a specific proteins

Question 4

What is a genome

Answer 4

Entire set of genetic material in an organism

Question 5

Why is understanding the human genome important (3 marks)

Answer 5

search for genes linked to different types of disease
understanding and treatment of inherited disorders
use in tracing human migration patterns from the past.

Question 6

What is sexual reproduction

Answer 6

genetic information from two organisms are combined to produce offspring which are genetically different to either parent

Question 7

In sexual reproduction how does the mother and father produce gametes

Answer 7

meiosis

Question 8

What is asexual reproduction

Answer 8

One parent - no fusion of gametes - no mixing of genetic information - genetically identical offspring through mitosis

Question 9

Give two examples of sexual reproduction

Answer 9

sperm and egg cells in animals
* pollen and egg cells in flowering plants.

Question 10

What happens when a cell divides to form gametes (3 marks)

Answer 10

copies of the genetic information are made
* the cell divides twice to form four gametes, each with a single set of chromosomes
* all gametes are genetically different from each other

Question 11

Describe what happens from gametes meeting at fertilization to the embryo’s cell(4 marks)

Answer 11

Gametes join at fertilization to restore the normal number of
chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate to make up an organism

Question 12

How many times does the cell divide and how many cells are produced

(meiosis)

Answer 12

2
4

Question 13

What does allele, phenotype and genotype mean

Answer 13

Allele: Different versions of a gene
Genotype: combination of alleles
Phenotype: Characteristic determined by alleles

Question 14

Give an example of homozygous recessive/dominant and heterozygous

(using b’s)

Answer 14

Homo.R - bb
Homo.D - BB
Hetero- Bb

Question 15

Phenotype/Genotype for Polydactyly

Answer 15

Phenotype - extra toes or fingers
Genotype - dominant allele

Question 16

Phenotype/Genotype for Cystic fibrosis

Answer 16

Phenotype - body producing excess amounts of mucus
Genotype - recessive allele

Question 17

For and against arguments for embryonic screening (6 marks)

Answer 17

For:
Help stop people from suffering
Treating disorders cost the government a lot of money
There are laws to stop it going too far i.e. parents can not select the sex of their baby unless for health reasons
Against:
Implies that people with genetic problems are ‘undesirable’ - could increase prejudice
Many come to a point where everyone wants to screen their embryos for more desirable phenotypes
Screening is expensive