Topic 6

Question 1

Describe the structure of DNA

Answer 1

A polymer made up of two strands coiled together in a double helix.

Question 2

What is a genome?

Answer 2

Entire set of genetic material of an organism.

Question 3

What is the monomer for DNA?

Answer 3

Nucleotides

Question 4

What are the parts of a nucleotide?

Answer 4

.Phosphate
.Sugar
.Base

Question 5

What is the code for an amino acid?

Answer 5

A sequence of 3 bases.

Question 6

What do the order of bases control?

Answer 6

The order in which amino acids are assembled which produce a particular protein.

Question 7

Explain the process of protein synthesis

Answer 7

Transcription
.A small copy of a gene is made= mRNA
.mRNA is only a single strand so can pass out of nucleus into cytoplasm

Translation
.mRNA attaches to a ribosome
.tRNA carries amino acids to the ribosome
.ribosome reads the mRNA and joins together correct amino acid in correct place
.this chain of amino acids is a poly-peptide which folds to form a protein

Question 8

What differences are there in structure between DNA and mRNA?

Answer 8

1) mRNA is shorter
2)mRNA is a single strand
3)Contains U base instead of T

Question 9

What are the 3 uses of proteins and what are their functions?

Answer 9

1) Enzymes- biological catalysts that speed up reactions in the body
2) Hormones- carry messages around the body
3) Structural proteins which are physically strong (e.g. collagen to strengthen ligaments)

Question 10

What’s a mutation?

Answer 10

A change to a base.

Question 11

True or false: Most mutations have an effect on a protein
Explain.

Answer 11

False because sometime a base might have changed but doesn’t change the amino acid sequence because different bases can sometimes code for the same amino acid

Question 12

What does changing the shape of a protein do?

Answer 12

Changes it’s function

Question 13

Give an example of when a mutation that changes the shape of a protein can have a dramatic effect?

Answer 13

Active site of an enzymes might change so can’t attach to substrate.

Question 14

What do non-coding chromosomes do?

Answer 14

Control if a gene is expressed or not (turn it on or off)

Question 15

What might a mutation to a non-coding chromosome do? Use an example.

Answer 15

Might switch on a gene that should be turned off e.g. uncontrolled mitosis leading to cancer.

Question 16

Explain the two types of mutations that can change more than one amino acid because it has a knock-on effect

Answer 16

Insertion- a new base is inserted into DNA base sequence
Deletion- a random base in the DNA sequence is changed to a different base

Question 17

Explain the type of mutation that only changes one amino acid because it doesn’t have a knock on effect

Answer 17

Substitution- a random base is changed to a different base

Question 18

What are gametes?

Answer 18

The reproductive cells

Question 19

How many chromosomes are in each gamete and why?

Answer 19

23 so that when the egg and sperm cell fuse it makes the whole amount (46)

Question 20

What are the gametes in plant reproduction?

Answer 20

Egg cell
Pollen

Question 21

Who reproduces asexually?

Answer 21

Bacteria, some plants, some animals

Question 22

Does ASEXUAL reproduction happen my mitosis or meiosis?

Answer 22

MITOSIS

Question 23

Does SEXUAL reproduction happen by mitosis or meiosis?

Answer 23

MEISOSIS

Question 24

Where does meiosis occur in the human body?

Answer 24

Males- testes
Females- ovaries

Question 25

Explain the process of meiosis

Answer 25

1)The chromosomes are copied 2)The cells divides into two daughter cells 3)These two cells divide again to produce in total 4 genetically different cells 5)Each cell has half the number of chromosomes as original cell

Question 26

What are the advantages of SEXUAL reproduction?

Answer 26

1) Variation in offspring 2) If environment changes, variation in offspring gives survival advantage by natural selection

Question 27

What are the ASEXUAL reproduction?

Answer 27

1)Less time 2)Less energy 3)Only one parent needed

Question 28

Give some examples of organisms that reproduce both sexually and asexually

Answer 28

Malarial protists reproduce asexually in the human host but sexually in the mosquito. Strawberry plants

Question 29

Explain 2 inherited disorders and the type of allele they are caused by.

Answer 29

Cystic Fibrosis (caused by recessive allele) =disorder of the cell membrane causing a lot of thick mucus being produces in the air passages and the pancreas. Polydactyl (caused by a dominant allele) =having extra fingers or toes

Question 30

What are the pros of embryo screening?

Answer 30

1)help stop people suffering 2)treating disorders costs the government and taxpayers a lot of money

Question 31

What are the cons of embryo screening?

Answer 31

1) expensive to carry out 2)risk of damaging the embryo 3)may be seen as unethical as embryos cannot consent

Question 32

Explain the theory of evolution by natural selection (Charles Darwin)

Answer 32

.Organisms with suitable characteristics for the environment are more likely to survive and reproduce -passing on gene that made them successful to the offspring .Organisms that are less well adapted are less likely to survive and reproduce so less likely to pass down genes to next generation .Over multiple generations, beneficial characteristics become more common and species evolves

Question 33

How does a new species occur?

Answer 33

.Organisms with suitable characteristics for the environment are more likely to survive and reproduce -passing on gene that made them successful to the offspring .Organisms that are less well adapted are less likely to survive and reproduce so less likely to pass down genes to next generation .Over multiple generations, the phenotype of an organism an change so much that it becomes a new species and cant breed with other species