B1 You And Your Genes

Question 0

Where do you find the instructions for how an organism develops?

Answer 0

In the nucleus of a cell

Question 1

What is a gene?

Answer 1

A small section of the DNA that makes up chromosomes in the nuclei of cells

Question 2

Explain the function of a gene?

Answer 2

They instruct the cell how to make proteins

Proteins can be structural e.g. Keratin in hair or enzymes e.g. Amylase

Question 3

Which cells have only a copy of one chromosome from each pair?

Answer 3

Sex cells (sperm and egg cells)

Question 4

What is another word for sex cells

Answer 4

Gametes

Question 5

What sex chromosomes do males have?

Answer 5

XY

Question 6

What sex chromosomes to females have?

Answer 6

XX

Question 7

What chromosome pair do you find the instructions for sex-determination

Hint: this is where the cell knows if you are going to be XX (girl) or XY (boy)

Answer 7

Chromosome pair 23

Question 8

How many chromosomes does a diploid cell have?

Hint: diploid just means a full set of chromosomes….

Answer 8

23 pairs which is 46 chromosomes in total

Question 9

How many chromosomes do haploid cells have?

Hint: haploid means a half set of chromosomes, one from each pair

Answer 9

23 chromosomes

Question 10

Where do the pairs of chromosomes come from?

Answer 10

One chromosome from mothers egg cell and one chromosome from fathers sperm cell

Question 11

What are alleles?

Answer 11

Different versions of a gene.

Example: we may inherit the short nose gene from our father and the long nose gene from our mother- if the short nose gene is DOMINANT then we will have a short nose

Question 12

What does homozygous mean?

Answer 12

That a person carries two copies of the same allele for any gene

Question 13

What does heterozygous mean?

Answer 13

A person carries two different alleles for any gene

Question 14

Why do offspring (children) look similar to their parents?

Answer 14

They have a combination of alleles from their mothers and fathers when an egg cell is fertilised by a sperm cell

Question 15

Give an example of a characteristic in humans that is determined by several genes working together?

Answer 15

Eye colour or blood group

Question 16

How many alleles are there usually on each gene?

Answer 16

Two

One from egg cell (mum) the other from sperm cell (dad)

Question 17

Explain why you don’t look the same as your brother or sister when you have the same parents?

Answer 17

Each person inherits a different combination of maternal and paternal genes during fertilisation and therefore shows different characteristics

Question 18

What is genotype?

Answer 18

The combination of alleles for a gene usually written as letters

E.g. Tt, tt or TT are all genotypes, they show us what alleles are present

Question 19

If a genotype is Tt and the gene it is coding for is being tall, what does the T mean?

Answer 19

The capital letter T means the allele is dominant- if a person has this allele it doesn’t matter what the other allele is because T is dominant and therefore the person will be tall

Question 20

If the alleles for foot length are F for big feet and f for small feet.
Mum is Ff and dad is Ff what combination of alleles might their child have and what is the % chance of them having a child with small feet?

Answer 20

Mum has F and f

Dad has F and f

Combinations FF, Ff, fF, ff
75% chance of big feet 25% of small feet as you would need to have two recessive alleles ff to have small feet. The presence of F in any genotype would mean you have big feet as it is the dominant allele