b13 - reproduction

Question 1

define allele

Answer 1

• a form or version of a gene
• you have two copies of each gene, one from each parent and these are alleles

Question 2

define asexual reproduction

Answer 2

• does not involve fusion of gametes
• all information comes from one parent
• little variation

Question 3

define sexual reproduction

Answer 3

• invoes fusion of gametes
• mixing of genetic information so more variation

Question 4

how are gametes formed?

Answer 4

by meiosis
- this process produces gametes (chromosome number halved)

Question 5

what happens when 2 gametes fuse?

Answer 5

fertilisation, a zygote is made and full chromosome number restored

Question 6

what are the sex cells in animals?

Answer 6

egg cells and sperm

Question 7

what are the sex cells in plants?

Answer 7

egg cells and pollen

Question 8

what happens during meiosis?

Answer 8

1) genetic material copied, chromosomes double
2) cell divides twice to form 4 gametes with single set of chromosomes
- all gametes are genetically different from eachother and from the parent cell

Question 9

how does mitosis link to meiosis?

Answer 9

once gametes (made from meiosis) fuse together, a new individual develops as this cell repeatedly divides by mitosis

Question 10

give 4 advantages of asexual reproduction

Answer 10

• only one parent needed
• more time and energy efficient
• faster than meiosis
• identical offspring produced

Question 11

give 2 disadvantages of asexual reproduction

Answer 11

• little variation
• all offspring are affected if environmental conditions change

Question 12

give 3 advantages of sexual reproduction

Answer 12

• variation
• if environment changes, variation given a survival advantage by natural selection
• natural selection can be accelerated by humans in selective breeding to increase food production

Question 13

disadvantages of sexual reproduction

Answer 13

• two gametes/ parents needed
• takes time, energy to find mate/spread gametes
• often slower than asexual reproduction

Question 14

give 3 organisms that reproduce using both methods

Answer 14

1) malarial parasites
2) fungi
3) flowering plants

Question 15

what is genetic material made up of?

Answer 15

deoxyribonucleic acid (DNA)

Question 16

define the structure of the DNA

Answer 16

• polymer (long molecule)
• double helix structure

Question 17

where is DNA found?

Answer 17

chromosomes

Question 18

define a gene

Answer 18

small section of DNA on chromosome

Question 19

define ‘genome of an organism’

Answer 19

entire genetic material of that organism

Question 20

why is it helpful to know the human genome?

Answer 20

• helps search for genes linking to differenct types of disease
• helps understand and treat inherited disorders
• helps trace human migration

Question 21

what are the long strands of DNA made up of?

Answer 21

chains of alternating sugar and phosphate sections

Question 22

what is attatched to the sugar in DNA?

Answer 22

one of four bases: A, C, G or T

Question 23

what makes up a nucleotide molecule?

Answer 23

a sugar, a phosphate, a base

Question 24

what does the order of bases control?

Answer 24

controls order in which amino acids are joined together to form a particular protein

Question 25

define mutation

Answer 25

a change in the order of bases that causes the wrong protein to be made

Question 26

what is base C always linked to?

Answer 26

base G

Question 27

what is base T always linked to?

Answer 27

base A

Question 28

what happens during protein synthesis?

Answer 28

1) gene produces a protein template
2) template leaves nucleus through pore in membrane
3) template attaches to ribosome in cytoplasm
4) carrier molecules in cytoplasm carry a specific amino acid
5) carrier molecules attatch themselves to template in order defined by template
6) the amino acids they carry join together to form protein
7) protein chain detaches from carrier molecules and folds into specific shape
8) carrier molecules return to cytoplasm and pick up more amino acids

Question 29

define ‘gene expression’

Answer 29

when a gene codes for a protein that is synthesised in cell, gene is expressed

Question 30

what does DNA do?

Answer 30

• part of it codes
• non-coding part are involved in switching genes on and off

Question 31

how can expression of genes be affected?

Answer 31

variations in non-coding areas of DNA