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

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

Question 5

Outline the role of meiosis

Answer 5

1) Before the cells starts to divide, it duplicates its DNA (so there is enough for each new cell). One arm of each x-shaped chromosome is an exact copy of the other arm.
2) In the first division in meiosis the chromosomes line up in pairs in the centre of the cell. One chromosome in each pair came from the organism’s mother and one came from their father.
3) The pair are then pulled apart so each new cell only has one copy of each chromosome. Some of the father’s chromosomes and some of the mother’s chromosomes go into each new cell.
4) Each new cell will have a mixture of the mother’s and father’s chromosomes. Mixing up the genes creates genetic variation in the offspring.
5) In the second division the chromosomes line up again in the centre of the cell. The arms of the chromosomes are pulled apart.
6) You get four haploid daughter cells- these are the gametes. Each gamete only has a single set of chromosomes. The gametes are all 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 combines- makes the DNA stick
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.

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 to make the mRNA. Base pairing between the DNA and RNAensures 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) Amino acids are brought to the ribosome by another RNA molecule called transfer RNA (tRNA).
2) The order in which the amino acids are brought to the ribosome matches the order of the base triplets in mRNA. Base triplets in mRNA are also known as codons.
3) Part of the tRNA’s structure is called an anticodon- it is complementary to the codon for the amino acid. The pairing of the codon and anticodon makes sure that the amino acids are brought to the ribosome in the correct order.
4) The amino acids are joined together by the ribosomes. This makes 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, the phenotype of the organism may be affected by how much of it is made.

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 Mendel’s 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 fertilized 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 one 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(B) and I(O)

Question 31

Which alleles are co-dominant in blood type?

Answer 31

I(A) and I(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)

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 two 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 singe mutations affect phenotype

Question 39

What is the Human Genome Project?

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 what 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

1) Inherited disorders (e.g. cystic fibrosis) are caused by the presence of one or more faulty alleles in a person’s genome.
2) Scientists are now able to identify the genes and alleles that are suspected of causing an inherited disorder much more quickly than they could in the past.
3) Once an allele that causes an inherited disorder has been identified people can be tested for it and it may be possible to develop better treatments or even a cure for the disease.

Question 42

How can the HGP help discover new and better medicines?

Answer 42

1) Genome research has highlighted some common genetic variations between people. Some variations affect how our individual bodies will react to certain diseases and to the possible treatments for them.
2) Scientists can use this knowledge to design new drugs that are specifically tailored to people with a particular genetic variation. This can also determine how well an existing drug will work for an individual. Tests can already whether or not someone with breast cancer will respond to a particular drug, and what dosage is most appropriate for certain drug in different patients.
3) Knowing how a disease affects us on a molecular level should make it possible to design more effective treatments with fewer side – effects.

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)