Genetics 101

Question 1

What is DNA?

Answer 1

DNA is a molecule found in the nucleus of every cell. It contains sequences of 4 bases (A,C,T,G) which code for the genetic material.

Question 2

What is a Gene?

Answer 2

A gene is specific sequence in DNA that codes for a particular characteristic.

Question 3

What does a base sequence do?

Answer 3

Bases tell the amino acids which order to go in.

Question 4

What are Alleles?

Answer 4

Alleles are an alternative form of gene that occupies the same location (locus) on a chromosome. It has slightly different base sequence which codes for a slightly different trait. They code for the phenotype. An individual has two alleles on homologous chromosomes for every characteristic.

Question 5

What is a phenotype?

Answer 5

Phenotypes are the outward appearance of the genotype.

Question 6

What is a genotype?

Answer 6

The genotype of an offspring is determined by a combination of the parents genotypes and alleles.

Question 7

What is a mutation?

Answer 7

A mutation is a permanent change in the base sequence that occurs when DNA replicates. It results in a new allele. It has to be present in the gametes for it to be inheritable.

Question 8

What is genetic variation?

Answer 8

Genetic variation results from differences in the DNA between a species.

Question 9

What is the amount of genetic variation determined by?

Answer 9

It is determined by the number of different alleles in the population.

Question 10

What is crossing over?

Answer 10

Crossing over is the exchange of DNA material between non-sister homologous chromosomes.

Question 11

What does crossing over produce?

Answer 11

Crossing over produces new combinations of alleles on the chromosome of the haploid cell.

Question 12

What is independent assortment?

Answer 12

Independent assortment is where chromosomes move randomly to seperate poles. This leads to gametes that contain a unique combination of alleles.

Question 13

What is mitosis?

Answer 13

Mitosis is the cell division of somatic cells.

Question 14

How many daughter cells are in meiosis?

Answer 14

4 haploid cells

Question 15

What does haploid mean?

Answer 15

Single set of chromosomes

Question 16

What does diploid mean?

Answer 16

A full set of chromosomes.

Question 17

What is inheritable variation?

Answer 17

Phenotype differences are encoded in the DNA of all cells, these difference can be passed on to offspring.

Question 18

What needs to happen in order to for variation to be inherited?

Answer 18

The gamete that is being fertilised or is fertilised needs to contain the variation, this will passed down to the zygote.

Question 19

What are some causes of non-inheritable variation?

Answer 19

Environment causes.

Question 20

What are some causes of non-inheritable variation?

Answer 20

Environment causes.

Question 21

A square on a pedigree chart is?

Answer 21

Male

Question 22

A circle on a pedigree chart is?

Answer 22

Female

Question 23

A shaded shape on a pedigree chart is?

Answer 23

Effected.

Question 24

Recessive

Answer 24

Requires two recessive alleles (hh) to be expressed.

Question 25

Dominant

Answer 25

Masks recessive alleles which are always visible if present (HH,Hh)

Question 26

Punnet Squares

Answer 26

Each mating is a unique opportunity for the baby to have either a 25% chance of ‘aa’ or a 75% chance of ‘Aa’

Question 27

What is genetic variation?

Answer 27

Is the sum total of all the characteristics in a species. This is important so the species have a more diverse range of characteristics, and therefore will not be susceptible to diseases.