Topic 3- Genetics

Question 1

What are gametes?

Answer 1

sex cells (sperm and egg)

Question 2

What is a zygote?

Answer 2

fertilized egg

Question 3

What are the stages of mitosis?

Answer 3

interphase, prophase, metaphase, anaphase, telophase, cytokinesis

Question 4

What is meiosis?

Answer 4

a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes

Question 5

Describe meiosis

Answer 5

• DNA duplicates
• divides into 2 cells, each with one full set of DNA
• crossing over occurs, mixing the DNA of the mother and father
• the second divisions happen, leaving 4 daughter cells, each with half a set of DNA, and each with different DNA

Question 6

What are the advantages of asexual reproduction?

Answer 6

Identical offspring, no special cells required, speedy process, lots of offspring, don’t need a mate so can quickly take advantage of good conditions

Question 7

What are the disadvantages of asexual reproduction?

Answer 7

no genetic variation - extinction is more likely if there is a change in the environment as the entire population will be affected.

Question 8

What are the advantages of sexual reproduction?

Answer 8

Diverse offspring making it more likely that some of the population would survive if there were a change in the environment, adaptability, can live in different environments

Question 9

What are the disadvantages of sexual reproduction?

Answer 9

• slow reproductive rate
• smaller number of offspring
• more energy needed

Question 10

What are the bases of DNA?

Answer 10

Adenine, Thymine, Guanine, Cytosine

Question 11

What are the pairs of bases?

Answer 11

A with T and G with C

Question 12

What is the structure of DNA?

Answer 12

A double helix made from four bases, with a sugar phosphate backbone and weak hydrogen bonds between pairs of bases

Question 13

How can you extract DNA from fruit cells?

Answer 13

1. Mash strawberries and out in beaker containing detergent and salt; mix well
2. Detergent will break down cell membranes to release DNA; salt will make DNA clump together
3. Filter mixture to get froth and big insoluble bits of cell out
4. Gently add some ice-cold alcohol to filtered mixture
5. DNA will come out of solution as it’s not soluble in cold alcohol; will appear as stringy white precipitate that can be fished out with glass rod

Question 14

What is transcription?

Answer 14

synthesis of an RNA molecule from a DNA template

Question 15

What is translation?

Answer 15

the decoding of an mRNA message into a protein

Question 16

Describe transcription

Answer 16

RNA polymerase binds to DNA, separates the strands, then uses a strand as a template to assemble mRNA as it moves along.
Then, the mRNA will move out of the nucleus to a ribosome

Question 17

Describe translation

Answer 17

The bases are read in triplets, known as codons, with each codon coding for an amino acid. The amino acids are brought by the tRNA to the mRNA, and form a chain. Then the polypeptide chain folds to form a protein. The shape it folds into (dependent on the order of amino acids), determines the function.

Question 18

What is a mutation?

Answer 18

A rare, random change in genetic material that can be inherited

Question 19

How can a mutation in the non-coding DNA affect the phenotype?

Answer 19

It could affect how well the RNA polymerase can bind to it during transcription, therefore affecting how much mRNA is transcribed, and therefore the wrong amino acid may be brought.

Question 20

What are alleles?

Answer 20

different versions of the same gene

Question 21

What is a genotype?

Answer 21

genetic makeup of an organism

Question 22

What is a phenotype?

Answer 22

physical characteristics of an organism

Question 23

What did Medel conclude?

Answer 23

• characteristics are determined by “heredititary units”
• hereditary units are passed on unchanged from both parents, one from each parent
• hereditary units can be dominant or recessive, if an individual has both, the dominant will be shown in the phenotype

Question 24

How can genetic disorders be sex-linked?

Answer 24

As the Y-chromosome is shorter, it carries fewer genes. This means that if a recessive allele for a disease is carried in the X-chromosome, there may be no allele, dominant or recessive in the Y-chromosome which could prevent the expression of this disease in the phenotype. This makes it more likely that men will get certain recessive genetic characteristics.

Question 25

What are the alleles for blood type?

Answer 25

IA, IB, IO

Question 26

Which blood type alleles are codominant?

Answer 26

IA IB

Question 27

What does heterozygous mean?

Answer 27

two different alleles

Question 28

What does homozygous mean?

Answer 28

same alleles

Question 29

What is genetic variation?

Answer 29

differences that occur in individuals within a species due to having different alleles

Question 30

What is environmental variation?

Answer 30

characteristics inherited from environment and lifestyle

Question 31

What is the Human Genome Project?

Answer 31

Scientists in 18 different countries collaborated to decode the human genome. This is the order of bases on all the human chromosomes. The project was completed quickly because so many scientists worked on it at the same time. The work was published in 2003.

Question 32

What are the applications of the research produced by the human genome project?

Answer 32

Prediction and prevention of diseases, testing and treatment for inherited disorders, as well as new and better medicines, as scientists can predict better how people will react to medicine, as well as what an appropriate dose would be.

Question 33

What are the possible drawbacks of the research produced by the human genome project?

Answer 33

• increased stress if people know they have the gene for a genetic disorder
• gene-ism: people with genetic disorders may come under pressure not to have children
• discrimination by insurers and employers