P2- Topic 6- Inheritance, Variation and Evoloution 2022

Question 1

What is sexual reproduction? 3

Answer 1

Type of reproduction

the joining of male and female gametes, each containing genetic information from the mother or father.

Sperm and egg cells in animals

Pollen and egg cells in flowering plants

Question 2

What are gametes?2

Answer 2

Sex cells (sperm cells and egg cells in
animals, pollen and egg cells in flowering
plants).

● Haploid (half the number of chromosomes)

Question 3

what does meiosis lead to 3

Answer 3

formation of four non-identical cells from one cell

Chromosome number is halved.

Involves two divisions

Question 4

What is asexual reproduction?

Answer 4

Involves mitosis only.

Produces genetically identical offspring
known as daughter cells.

Question 5

what happens in meiosis 4

Answer 5

a cell divides to form gametes

copies genetic information

cell divides 2x to form four gametes, each with a single set of
chromosomes

all gametes are genetically different from each other.

Question 6

Why is meiosis important for sexual

reproduction? (2)

Answer 6

increases genetic variation.

ensures the zygote formed at fertilisation is diploid

Question 7

Describe fertilisation and its resulting

outcome 2

Answer 7

Gametes join together to restore the normal
number of chromosomes and the new cell then
divides by mitosis (which increases the number
of cells).

As the embryo develops, cells differentiate.

Question 8

Why is understanding the human genome

important?4

Answer 8

The whole human genome has been studied and is
important for the development of medicine in the future

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 9

Define genome

Answer 9

The entire genetic material of an organism.

Question 10

Describe the structure of DNA4

Answer 10

• polymer
• made up of two strands
• forming a double
  helix.
• DNA contained in structures called chromosomes

Question 11

What are DNA nucleotides made up of?3

Answer 11

common sugar

phosphate group

one of four different bases attached to the sugar. A,T,C,G

Question 12

Define gene

Answer 12

-a small section of DNA on a chromosome.

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

Question 13

what are the monomers of DNA?

Answer 13

Nucleotides

Question 14

Describe how nucleotides interact to form a molecule
of DNA (3)

Answer 14

Sugar and phosphate molecules join to form a
sugar-phosphate backbone in each DNA strand.

Base connected to each sugar.

Complementary base pairs (A pairs with T, C pairs with G)
joined by weak hydrogen bonds

Question 15

Explain how a gene codes for a protein 3

Answer 15

A sequence of three bases in a gene forms a triplet.

● Each triplet codes for an amino acid.

● The order of amino acids determines the structure
(i.e. how it will fold) and function of protein formed

Question 16

What is protein synthesis?

Answer 16

The formation of a protein from a gene

Question 17

What are the two stages of protein synthesis?

Answer 17

1. Transcription

2. Translation

Question 18

What does transcription involve?

Answer 18

The formation of mRNA from a DNA

template

Question 19

Outline transcription 4

Answer 19

1. DNA cannot move out of
   the nucleus as it is too big.
2. The two strands pull apart from each other, and mRNA nucleotides
   match to their
   complementary base on the strand.
3. mRNA nucleotides joined together, creating a new
   strand called the mRNA strand. This is a template of the original DNA.
4. The mRNA then moves out of the nucleus to the cytoplasm and onto
   structures called ribosomes.

Question 20

outline translation 4

Answer 20

1. mRNA attaches to a ribosome.
2. Ribosome reads the mRNA bases in triplets. Each triplet codes
   for one amino acid which is brought to the ribosome by a tRNA molecule (carrier molecule).
3. A polypeptide chain is formed from the sequence of amino
   acids which join together

Question 21

What is a mutation? 2

Answer 21

A random change in the base sequence of DNA

results in no change to the protein coded for, or
genetic variants of the protein (slight alteration but
appearance and function remain)

Question 22

Describe the effect of a gene mutation in coding DNA 2

Answer 22

the protein structure and function may change (an enzyme may no longer
fit its substrate binding site or a structural protein may lose its
strength).

● If a mutation does not change amino acid sequence, there is no effect on protein structure or function

Question 23

What is non-coding DNA?

Answer 23

DNA which does not code for a protein but controls which genes are expressed

Question 24

Describe the effect of a gene mutation in non-coding DNA (2)

Answer 24

Gene expression may be altered, affecting protein production and the resulting phenotype (physical charecteristics)

Question 25

What are alleles?

Answer 25

Different versions of the same gene

Question 26

what is a recessive or dominant allele 2

Answer 26

d-A version of a gene where only one copy is needed for it to be expressed

r-A version of a gene where two copies are needed for it to be expressed

Question 27

what does it mean for a organism to be homozygous or heterozygous 2

Answer 27

homo-When an organism has two copies of the same allele (two recessive or two
dominant)

hete-When an organism has two different versions of the same gene (one dominant and one recessive).

Question 28

what is a genetype and example

Answer 28

The genes present for a trait

The combination of alleles an individual has, e.g. Aa

Question 29

What is the phenotype? and example 2

Answer 29

The visible characteristic eye colour

Question 30

What is the problem with single gene crosses?

Answer 30

Most characteristics are controlled by multiple alleles rather than just one.

Question 31

Give 2 examples of inherited disorders and allele cause4

Answer 31

Polydactyly (having extra fingers or toes)

dominant allele.

Cystic fibrosis (a disorder of cell membranes

recessive allele.