Genetics

Question 1

What is sexual reproduction?

Answer 1

Where genetic information from two organisms (a mother and father) is combined to produce offspring which are genetically different to either parent/

Question 2

What is meiosis?

Answer 2

A type of cell division that only happens in the reproductive organs (testes and ovaries)
It produces gametes

Question 3

What happens in the first divisionnof meiosis?

Answer 3

• The cell duplicates its DNA, one arm of each x-shaped chromosome is a exact copy of the other arm
• The chromosomes line up in pairs in the centre of the cell. One chromosome from each pair came from the mother and father
• The pairs are pulled apart, so each new cell has only one copy of each chromosome some from the mother and some to the father go into each new cell
• The mix creates genetic variation

Question 4

What happens in the second division of meitosis?

Answer 4

The chromosomes line up again in the centre of the cell
The arms of the chromasomes (called chromatids) are pulled apart

Question 5

What do you end up with in meiosis?

Answer 5

You get four haploid daughter cells - these are gametes.
Each gamete only has a single set of chromosomes
The gametes are all genetically different

Question 6

What is DNA made up of?

Answer 6

DNA strands are polymers (a large molecule made up of many smaller molecules) made up of lots of repeating units called nucleotides

Question 7

What does a nucleotide contain?

Answer 7

Each nucleotide consists of one sugar molecule, (pentagon) one phosphate molecule (circle) and one ‘base’ (square)

Question 8

What forms the backbone of the DNA strand?

Answer 8

The sugar and the phosphate molecules

Question 9

What are the 4 bases that join to each sugar?

And what are the pair

Answer 9

A (Adenine) and T (Thymine)
G (Guanine) and C (Cytosine)
Complemenatry base pairs

Question 10

How is DNA made up and the shape?

Answer 10

A DNA molecule has two strands coiled up together in the shape of a doublr helix (double strand spiral)
Each pair links to a base on the opposite stand in the helix

Question 11

What are the complementary base pairs joined together by?

Answer 11

Weak hydrogen bonds

Question 12

What is a chromosome?

Answer 12

Chromosomes are long, coiled up molecules of DNA that are found in the nucleus of eukaryotic cells

Question 13

What is a gene?

Answer 13

A gene is a section of DNA on a chromosome that codes for a particular protein

Question 14

What does genome mean?

Answer 14

All of an organismas DNA makes up its genome

Question 15

How do you extract DNA from a fruit?

Answer 15

• Mash some strawberries and put it a beaker containing a solution of detergent and salt. Mix well
• The detergent will break down the cell membrane to release the DNA
• The salt will make the DNA stick together
• Filter the mixture to get the froth and the big, insoluble bits of the cell out
• Gently add some ice-cold alcohol to the filtered mixture
• The DNA will start to come out of the solution as it’s not soluble in cold alcohol. It will appear as a stringy white precipitate (a solid) that can carefully be fished out using a glass rod

Question 16

What is a allele?

Answer 16

Different version of the same gene

Question 17

What does homozygous mean?

Answer 17

An organism has two alleles for a particular gene that are the same

Question 18

What does heterozygous mean?

Answer 18

Two alleles for a particular gene that are different

Question 19

Explain dominant and recessive alleles

Answer 19

Dominant alleles (C) over rule recessive alleles (c)
So if an organism has one dominant and one recessive then the dominant allele will determine what characteristic is present

Question 20

What is your genotype and pheynotype?

Answer 20

The combination of alleles you have is your genotype

Your alleles determing what characteristics you have is your phenotype

Question 21

What does monohybrid inheritance mean?

Answer 21

The inheritance of a single characteristic