B3 Genetics

Question 1

What is a gamete?

Answer 1

Reproductive cells e.g. sperm and egg cellsW

Question 2

What is a zygote?

Answer 2

A fertilised egg

Question 3

What are the processes in meiosis?

Answer 3

1. The chromosomes make identical copies of themselves
2. Similar chromosomes pair up
3. Pairs of chromosomes divide
4. The chromosomes then divide again producing four haploid cells

Question 4

What is asexual reproduction?

Answer 4

When cells divide by mitosis, which are genetically identical to the parent cell

Question 5

What is sexual reproduction?

Answer 5

Meiosis where genetically identical haploid gametes fuse to form a diploid cell at fertilisation

Question 6

What are the advantages of asexual reproduction?

Answer 6

1. Can produce lots of offspring very quickly
2. Only one parent is needed

Question 7

What are the disadvantages of asexual reproduction?

Answer 7

1. There is no genetic variation between offspring in the population

Question 8

What are the advantages of sexual reproduction?

Answer 8

1. Creates genetic variation in the population

Question 9

What are the disadvantages of sexual reproduction?

Answer 9

1. Takes more time and produces fewer offspring
2. Two parents are needed for sexual reproduction

Question 10

What are DNA strands made of?

Answer 10

Nucleotides

Question 11

What is in a nucleotide?

Answer 11

A phosphate group, a sugar and a base

Question 12

What are the four different bases?

Answer 12

A (Adenine), T (Thymine), C (Cytosine), G (Guanine)

Question 13

What are the base pairs joined together by?

Answer 13

Weak hydrogen bonds

Question 14

How do you extract DNA from fruit cells?

Answer 14

1. Mash some fruit and put in a beaker of salt and detergent (detergent breaks down cell membrane)
2. Filter the mixture
3. Cool in an ice bath and add ethanol
4. DNA will become a white precipitate

Question 15

What is a gene?

Answer 15

A section of DNA that codes for a particular protein

Question 16

What occurs in transcription?

Answer 16

1. RNA polymerase binds onto the non-coding region of a gene
2. It unzips the DNA and passes along a DNA strand, adding complementary base pairs to the gene
3. Once made, the mRNA strand moves out of the nucleus, into the ribosomes

Question 17

What occurs in translation?

Answer 17

1. A codon codes for an amino acid
2. The anticodon is complementary to a codon which is part of the tRNA molecule
3. The amino acids form a polypeptide chain

Question 18

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

Answer 18

1. The RNA polymerase may not bind properly to the DNA strand
2. It affects how much mRNA is transcribed

Question 19

What did Mendel do?

Answer 19

1. He bred a tall pea plant and a short pea plant with all the offspring being tall
2. He bred two of these tall offspring plants together and found that for every small plant, there were three tall plants

Question 20

What are two different alleles?

Answer 20

Heterozygous

Question 21

What are two dominant alleles?

Answer 21

Homozygous dominant

Question 22

What are two recessive alleles?

Answer 22

Homozygous recessive

Question 23

What chromosomes do males have?

Answer 23

XY

Question 24

What chromosomes do females have?

Answer 24

XX

Question 25

What are the positives gained from the Human Genome Project?

Answer 25

1. Prediction and prevention of disease 2. Testing and treatment for inherited diseases 3. New and better medicines