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 are examples of asexual reproduction?

Answer 2

• Strawberry plants send out runners which touch the ground and grow a new plant
• daffodils produce lots of smaller bulbs that can grow into new pants
• many fungi reproduce asexually by spores
• Malarial protists reproduce asexually when they are in the human host

Question 3

What does sexual production involve?

Answer 3

• 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 4

How is meiosis carried out?

Answer 4

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 5

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

Answer 5

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 6

What are the 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 speeded up by humans in selective breeding to increase food production

Question 7

What are the advantages of asexual reproduction?

Answer 7

• 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 8

What are examples of times when organisms using both asexual reproduction and sexual reproduction depending on the circumstance?

Answer 8

• many fungi reproduce asexually by spores but reproduce sexually to give variation
• malaria parasites reproduce asexually in the human host, but sexually in the mosquito
• many plants produce seeds sexually but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils

Question 9

What is the genome of an organism?

Answer 9

the entire genetic material of that organism

Question 10

What is a gene?

Answer 10

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

Question 11

The whole human genome has now been studied.

What does this enable us to do?

Answer 11

• 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 12

Ho many different repeating nucleotides is DNA made from?

Answer 12

4

Question 13

What do nucleotides consist of?

Answer 13

common sugar, phosphate and one of the 4 bases

AGCT

Question 14

What do the order of bases do?

Answer 14

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

Question 15

which bases are attracted to each other

Answer 15

C=G

A= T

Question 16

How are proteins made?

Answer 16

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 17

What is a mutation?

Answer 17

a random change in DNA structure

Question 18

Why are most mutations harmless?

Answer 18

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

Question 19

What increases the rate of mutations?

Answer 19

• certain chemicals and high-energy radiation

Question 20

What happens if any base in the DNA is changed?

Answer 20

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

Question 21

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

Answer 21

An enzyme may no longer fit the substrate binding site

a structural protein may lose its strength.

Question 22

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

Answer 22

it may affect how the genes are expressed

Question 23

What is an allele

Answer 23

an alternate form of a particular gene

Question 24

What is a phenotype?

Answer 24

How the alleles are expressed

Question 25

What does homozygous mean?

Answer 25

when two alleles are the same

Question 26

What does heterozygous?

Answer 26

alleles are different

Question 27

What are most characteristics the result of?

what is it called when only one gene is involved?

Answer 27

multiple genes interacting, rather than a single one

monohybrid inheritance

Question 28

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

Answer 28

dominant

Question 29

What type of allele is Cystic fibrosis?

Answer 29

recessive allele

Question 30

What is embryo screening?

Answer 30

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 31

What are the positives of embryo screening?

Answer 31

• 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 32

What are the cons of embryo screening?

Answer 32

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

Question 33

what are the chromosomes for female and male

Answer 33

female = XX

Male = XY