Topic 3 - Genetics

Question 1

What are some advantages to asexual reproduction?

Answer 1

1) Organisms can colonise areas very quickly because the process is really fast.
2) Only one parent is needed - organisms can reproduce whever conditions are favourable and do not have to wait for a mate

Question 2

What are some disadvantages to asexual reproduction?

Answer 2

Disease can spread rapidly because there is no variation in the population. This means it is likely no organism will be resistant to a disease and this may kill of a whole species

Question 3

What are some advantages to sexual reproduction?

Answer 3

Variation - (can lead to survival)

Question 4

What are some disadvantages to sexual reproduction?

Answer 4

1) Takes more time and energy (having to attract mates) so fewer organisms are produced in their lifetime
2) Two parents are needed, this can be a problem for isolated individuals

Question 5

Outline the role of meiosis

Answer 5

Meiosis takes place in the ovaries and testes and it produces 4 haploid daughter cells - gametes. These gametes only have a single set of chromosomes that are genetically different

Question 6

Describe the structure of DNA?

Answer 6

1) DNA strands are polymers made up of nucleotides
2) nucleotides consist of a phosphate and sugar backbone and a base.
3) the four bases are A and T, and C and G and they are joined together by weak hydrogen bonds
4) Two DNA strands coil together to form the shape of a double helix

Question 7

What is a genome?

Answer 7

The entire DNA of an organism

Question 8

What is a gene?

Answer 8

A section of DNA that codes for a particular protein

Question 9

How can DNA be extracted from fruit?

Answer 9

1) crush up fruit
2) add salt to make sure the fruit is combined (salt is used to make the DNA stick together)
3) add detergent to break down cell membranes to release DNA
4) filter to get froth and insoluble bits out
5) add cold alcohol to separate DNA. it will appear as a white precipitate

Question 10

What do the order of bases in a gene determine?

Answer 10

the order of amino acids in a protein

Question 11

How are amino acids involved in giving enzymes their specific shapes?

Answer 11

Amino acids fold up to give each protein a different, specific shapes - so that they can carry out a specific functions. (enzymes)

Question 12

Describe transcription (making mRNA)

Answer 12

1. RNA polymerase binds to non coding DNA and moves along it (strands unzip)
   2) uses the coding DNA as a template for the mRNA. Base pairing between the DNA and mRNA so that the mRNA is complementary to the gene
   3) mRNA moves out of the nucleus and joins to a ribosome

Question 13

Describe translation

Answer 13

1) amina acids are brought to ribosomes by tRNA
2) order of amino acids matches the base triplets (codon) in mRNA.
3) anticodon in tRNA is complementary to codon for amino acids . This makes sure amino acids are brought to ribosome in correct order
4) the ribosomes joins the amino acids together to form a polypeptide (protein)

Question 14

How can non-coding DNA affect phenotype?

Answer 14

1) can affect how well RNA polymerase binds to DNA
2) affects how much mRNA is transcribed
3) therefore, affects how much of the protein is made.
4) affects phenotype depending on the function of the protein

Question 15

How can coding DNA affect phenotype?

Answer 15

• genetic variant in a base sequence can change the order of amino acids and change the shape of an enzyme
• may affect activity of enzyme

Question 16

Describe Mendels experiment

Answer 16

1) crossed tall and short pea plant
2) 4 tall pea plants were produced. he crossed 2 of the tall pea plants
3) found that 3 tall and 1 short plant were produced.
3: 1 ratio of tall to short plants

Question 17

What were the three conclusions Mendel made?

Answer 17

1. characteristics in plants are determined by ‘hereditary units’ (genes)
2. genes are passed on from parents unchanged.
3. genes can be dominant or recessive. if a dominant gene is presented, it will be expressed instead of the recessive gene

Question 18

Why was it difficult to understand his work at the time?

Answer 18

• No knowledge about DNA, genes and chromosomes

Question 19

What are alleles?

Answer 19

different versions of the same gene

Question 20

Where are our 2 versions of alleles located?

Answer 20

one on each chromosome in a pair

Question 21

which can overrule the other - dominant or recessive?

Answer 21

dominant

Question 22

what is heterozygous?

Answer 22

two alleles which are different

Question 23

What is homozygous?

Answer 23

two alleles that are the same

Question 24

What is a genotype?

Answer 24

the combination of alleles you have

Question 25

What is a phenotype?

Answer 25

our physical characteristics

Question 26

What are gametes?

Answer 26

The sperm and egg cells (haploid)

Question 27

What is a zygote?

Answer 27

a fertilised egg

Question 28

What is a chromosome?

Answer 28

a long coiled up molecule of DNA

Question 29

Why does sex determination depend on the male?

Answer 29

All eggs have an X chromosome but the sperm can have either an X chromosome or a Y chromosome. so sex determination depends on what chromosome the sperm carries

Question 30

What are the three alleles for blood type?

Answer 30

I(A), I(O), I(B)

Question 31

Which alleles are codominant in blood type?

Answer 31

I(A) and 1(B)

Question 32

Which allele is recessive in blood type?

Answer 32

I(O)

Question 33

How can you get blood type O

Answer 33

By having two of the recessive alleles - I(O) I(O)`

Question 34

What problems may arise due to the fact that males only have one x chromosome?

Answer 34

They might carry a faulty allele as they only have one copy of the allele on the x chromosome. This means that the characteristic will show even if it is recessive

Question 35

What would the chance of a child contracting colour blindness/haemophilia rise to if the child was a boy?

Answer 35

50 percent

Question 36

Are most characteristics controlled by a single gene or by several genes interacting?

Answer 36

Several genes interacting

Question 37

what three things cause variation?

Answer 37

1. Sexual reproduction (different alleles combining)
2. Mutations (causing different versions of the same genes)
3. environmental factors (e.g plants may grow/look differently depending on the conditions)

Question 38

To what extent can mutations affect phenotype?

Answer 38

• Most mutations have no effect on phenotyoes
• Some mutations have a small efect on phenotypes
• Very rarely do single mutations affect phenotype

Question 39

What is the Human Genome Projecr?

Answer 39

A project to find every singe human gene and identify the genes related to disease and how they could benefit in medicine

Question 40

How can the HGP predict and prevent diseases?

Answer 40

If doctors knew hat genes predisposed people to what diseases, we could all get individually tailored on the best diet and lifestyle to avoid our likely problems. Dr’s could also check us regularly to ensure early treatment if we do develop diseases were susceptible to

Question 41

How can HGP help testing and treatment for inherited disorders?

Answer 41

By mapping out the faulty genes, people can be tested for disorders and it may even be possible to find a treatment or even a cure for the disease

Question 42

How can the HGP help discover new and better medicines?

Answer 42

By finding genetic variations in people, scientists can use this to design new drugs that are tailored to people with a genetic variation. They can also determine how well a drug will work for someone and an appropriate dosage

Question 43

What are some drawbacks to the project?

Answer 43

1) increased stress (from paranoia)
2) gene-ism - people may come under pressure not to have children
3) Discrimination by employers and insurers (for having the genetic likelihood of contracting a disease)