B6: inheritance

Question 1

What is meiosis

Answer 1

Form of cell division involved in the formation of gametes (non identical haploid cells)

Question 2

What must occur prior to meiosis?

Answer 2

Interphase - copies of genetic information are made during this process.

Question 3

What happens in the first stage of meiosis?

Answer 3

Chromosomes (pairs) make copies of themselves (now have two of each pair)
Chromosomes pairs line up along cell eqautor and swap pieces of information
The pair of chromosomes are separated and move to opposite poles of the cell
Chromosome number is halved

Question 4

What happens in the second stage of meiosis?

Answer 4

Chromosomes line up along the cell equator (this happens in both cells)
The chromatids (single chromosome) are separated and move to opposite poles of the cell.
Cell divides
Four unique haploid gametes are produced

Question 5

What occurs at fertilisation?

Answer 5

The gametes join together to restore number of chromsones( 23 pairs rather than single). The new cell divides by mitosis to increase number of cells and produce a clump of identical cells (embryo).
As embryo develops, cells differentiate forming different cell types.

Question 6

Give 3 advantages of sexual reproduction

Answer 6

• Produces variation in offspring
• If the environment changes, variation gives a survival advantage by natural selection
• Natural selection can be speed up by humans in selective breeding to increase food production

Question 7

Give 3 advantages of asexual reproduction

Answer 7

• Only one parent needed
• Faster than sexual reproduction
• Requires less energy and time

Question 8

What is asexual reproduction?

Answer 8

Type of reproduction involving mitosis only that produces genetically identical offspring (daughter cells)

Question 9

Describe the circumstances in which malarial parasites reproduce sexually and asexually

Answer 9

Sexual in the mosquito
Asexual in the human host

Question 10

Describe the circumstances in which fungi reproduce sexually and asexually

Answer 10

Asexual by spores
Sexual to give variation

Question 11

Define genome

Answer 11

The entire genetic material of an organism

Question 12

Describe the structure of DNA

Answer 12

A polymer made up of molecules called nucleotides. There are 4 different nucleotides , however each of these consist of a sugar group and a phosphate group and ONLY THE BASE CHANGES. The 4 bases are: A, C, G,T.

(A pairs with T, C pairs with G)

Question 13

What is a gene

Answer 13

A small section of DNA on a chromosome that codes for a specific sequence of amino acids.

Question 14

Describe how nucleotides interact to form a molecule of DNA

Answer 14

• Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand.
• A base (c,g,a,t) will connect to the sugar
• Complementary base pairs are joined by week hydrogen bonds

Question 15

What is protein synthesis

Answer 15

The formation of a protein from a gene

Question 16

What are the two stages of protein synthesis?

Answer 16

1. Transcription: the formation of mRNA from a DNA template
   2.Translation: a ribosome joined amino acids in a specific order dictated by mRNA to form a protein.