DNA / Reproduction

Question 1

What distinguishes sexual reproduction? (6)

Answer 1

-requires two mates / gametes (egg and sperm)
-can cause variations
-not genetically identical with the parent
-inherits both DNA from both parents
-fertilisation
-mitosis

Question 2

What are the advantages and disadvantages of sexual reproduction?

Answer 2

Advantages:
- results in variation which helps the species to thrive and have the best chance of survival in different environments, eg, species can develop a certain characteristic or trait which prevents a whole population from being wiped out from a disease.

Disadvantages:
- inefficient for time and energy (needs to find a mate)

Question 3

What distinguishes asexual reproduction? (5)

Answer 3

-requires only one parent
-doesn’t result in variations
-mitosis and meiosis
-creates something genetically identical to its parent
-no fertilisation

Question 4

What are the advantages and disadvantages of asexual reproduction?

Answer 4

Advantages:
-energy and time efficient
-population can easily grow and recover from being affected by external changes.

Disadvantages:
-no variation so populations can be wiped out (greatly affected) by a disease.

Question 5

Explain how gametes are made:

Answer 5

Gametes are made via meiosis as they need to contain 23 chromosomes in their nucleus instead of 23 pairs found in mitosis.
1. the cell grows in size (interphase) and duplicates its other organelles except the chromosomes in the nucleus.
2. the pa

Question 6

What are homologous chromosomes?

Answer 6

When a chromosome from both maternal and paternal parents contain the same genes but different alleles (different versions of the gene)

Eg, one chromosomes from both the mum and dad can contain the gene for determining eye colour, but the mum may have a different allele than the dad. (blue and brown eyes)

Question 7

What can happen when a pair of homologous chromosomes attach to one another?

Answer 7

They can exchange genes between each other

Question 8

How many amino acids do humans have?

Answer 8

20

Question 9

Name and describe two processes occur in protein synthesis?

Answer 9

-transcription: when complimentary genes are copied from a single strand of DNA making a template of mRNA in the nucleus
-translation: when carrier molecules attach themselves to the template forming proteins.

Question 10

What is tRNA?

Answer 10

RNA which has three bases and an amino acid, it travels to its complimentary triple base sequence (codon) on the template in the ribosome and transfers/ leaves behind its amino acid, forming a long line of protein.

Question 11

Why are proteins so important in the body?

Answer 11

-transportation
-enzyme catalyse (chemical reaction such as in digestion)
-growth
-hormones

Question 12

What are the names of the bases?

Answer 12

-thymine
-adenine
-cytosine
-guanine

Question 13

How are proteins suited for their functions in general?

Answer 13

They contain a series of amino acids, which their order affects their shape to adapt to their function.

Question 14

What is in a nucleotide?

Answer 14

A phosphate, sugar and base.

Question 15

What is a gene?

Answer 15

A section of DNA that codes for synthesis.

Question 16

Describe a triplet code:

Answer 16

In a gene, the sequence of bases effects the sequence of bases forming a protein, to form a protein, three consecutive bases are grouped together to synthesise one type of protein.

Question 17

How would you extract DNA from a fruit?

Answer 17

1. remove the skin of a fruit
2. mash it in a tube beaker and with a cloth squeeze out its juice.
3. add salt and dish soap to it
4. add in hot water and wait 10 mins, constantly keeping the temperature constant with a surrounding water bath.
5. dribble in cold ethanol into the beaker.

Question 18

What does homologous mean?

Answer 18

Chromosomes that have an alike p

Question 19

What does recessive mean?

Answer 19

A genotype that occurs only if both alleles are present

Question 20

What does dominant mean?

Answer 20

A genotype that is expressed when at least one allele is present

Question 21

Describe the steps of protein synthesis:

Answer 21

1. DNA is unravelled into two separate strands by RNA polymerase
2. RNA Binds complimentary bases together from the original strand of DNA to form a template called transcription
3. The template then travels outside the nucleus to the ribosome
4. Here, translation happens where tRNA units that carry amino acids line up to their corresponding bases.
5. The amino acids then bind to each other with peptide bonds as the tRNA leaves forming a chain of amino acids that form a protein