Reproduction (Inheritance, Variation and Evolution pt1)

Question 1

What does Asexual reproduction involve?

Answer 1

• one parent
• no fusion of gametes ( no mixing of genetic information)
• the production of genetically identical offspring
• mitosis

Question 2

What does sexual production involve?

Answer 2

• the fusion of male and female gametes: sperm and egg; pollen and egg
• the mixing of genetic information leads to variation in offspring
• formation of gametes involves meiosis

Question 3

How is meiosis carried out?

Answer 3

1) Before the cell starts to divide, it duplicates its genetic information forming to armed chromosomes

2) Chromosomes pairs line up in the centre of the cell

3) Chromosomes part company and move to opposite poles

4) cell divides for the first time

5) Chromosomes line up again in the centre of the cell and the arms of the chromosomes are pulled apart

6) 4 haploid cells are formed, each half the number of chromosomes of the parent cell

all gametes are genetically different from each other

Question 4

How are the 23 pairs of chromosomes restored after meiosis and what happens after this process

Answer 4

in sexual reproduction, 2 gametes, one from male and one from female, join together to restore the full number of chromosomes = fertilisation

new cells divide by mitosis = embryo

cells become specialised by differentiated

Question 5

What are the advantages of sexual reproduction?

Answer 5

• produces variation in offspring
• if the environment changes, variation gives a survival advantage by natural selection
• natural selection can be speeded up by humans in selective breeding to increase food production

Question 6

What are the advantages of asexual reproduction?

Answer 6

• only one pared is needed
• more time and energy-efficient as they don’t need to find a mate
• faster than sexual reproduction
• many identical offspring can be produced when conditions are favourable

Question 7

What is the genome of an organism?

Answer 7

the entire genetic material of that organism

Question 8

What is a gene?

Answer 8

• a small section of DNA on a chromosome, which codes for a particular sequence of amino acids, to make a specific protein

Question 9

The whole human genome has now been studied.

What does this enable us to do?

Answer 9

• doctors can search for genes linked to different types of disorders
• helps scientists understand the cause of inherited disorders ad how to treat them
• we can use the human genome to trace human migration patterns from the past and how humans may have changed over time

Question 10

Ho many different repeating nucleotides is DNA made from?

Answer 10

4

Question 11

What do nucleotides consist of?

Answer 11

common sugar, phosphate and one of the 4 bases

(AGCT)

Question 12

What do the order of bases do?

Answer 12

it controls the order in which amino acids are associated to produce a particular protein

Question 13

which bases are attracted to each other

Answer 13

C=G

A= T

Question 14

How are proteins made?

Answer 14

1) proteins are synthesised on ribosomes, which is in the cytoplasm. During transcription, mRNA is used as a template to copy the base sequence of the gene in the nucleus
* mRNA is a single strand molecule

2) mRNA then passes out of the nucleus to the cytoplasm

3) Translation: mRNA molecule attaches to a ribosome.

4) carrier molecules (aka tRNA) then bring specific amino acids to add to the growing protein chain in the correct order

5) when the protein chain is finished, it folds up to form a unique shape

• this unique shape allows the proteins to do their job as enzymes, hormones or structural proteins such as collagen

Question 15

What is a mutation?

Answer 15

a random change in DNA structure

Question 16

Why are most mutations harmless?

Answer 16

because they don’t alter protein, or only alter it slightly so that its appearance or function is not changed

Question 17

What increases the rate of mutations?

Answer 17

• certain chemicals and high-energy radiation

Question 18

What happens if any base in the DNA is changed?

Answer 18

it may change the order of amino acids in the protein coded for by the gene

Question 19

What could happen when A few mutations code for an altered protein with a different shape.

Answer 19

An enzyme may no longer fit the substrate binding site

a structural protein may lose its strength.

Question 20

What happens if there is a mutation in the non-coding parts of DNA

Answer 20

it may affect how the genes are expressed

Question 21

What is an allele

Answer 21

an alternate form of a particular gene

Question 22

What is a phenotype?

Answer 22

How the alleles are expressed

Question 23

What does homozygous mean?

Answer 23

when two alleles are the same

Question 24

What does heterozygous?

Answer 24

alleles are different

Question 25

What are most characteristics the result of?

what is it called when only one gene is involved?

Answer 25

multiple genes interacting, rather than a single one

monohybrid inheritance

Question 26

What type of allele is Polydactyly (extra fingers or toes)?

Answer 26

dominant

Question 27

What type of allele is Cystic fibrosis?

Answer 27

recessive allele

Question 28

What is embryo screening?

Answer 28

During IVF, before embryo is implanted into the mother’s womb, a cell is removed from each embryo an is analysed for its genes

Embryos do not that have defective alleles are implanted into the women

Question 29

What are the positives of embryo screening?

Answer 29

• screening will stop people from suffering
• treating disorders cost the government a lot of money
• there are laws to stop it from going too far

Question 30

What are the cons of embryo screening?

Answer 30

• screening is expensive
• unethical = many embryos are destroyed
• some people may want to produce an embryo with desirable feature - unethical

Question 31

what are the chromosomes for female and male

Answer 31

female = XX

Male = XY