genetics

Question 1

Explain the role of meiotic cell division

Answer 1

• produces 4 daughter cells which are haploid (half number of chromosomes (23))
• these are gametes (gametes are genetically different)

Question 2

Describe DNA as a polymer made up of

Answer 2

a) repeating unit of nucleotides - sugar and phosphate groups, one of four bases on sugar
b) two strands coiled to form a double helix
c) strands linked by series of complementary base pairs, joined with hydrogen bonds

Question 3

Describe the genome as the entire DNA of an describe the genome and the gene

Answer 3

a) genome = all the DNA in an organism
b) gene = section of a DNA molecule - codes for a specific protein

Question 4

Explain how DNA can be extracted from fruit

Answer 4

1. mash strawberries put in detergent and salt solution beaker
   a) detergent breaks down cell membranes to release DNA
   b) salt makes DNA stick together
2. filter
   to get the froth and big - insoluble bits of cell out
3. gently add ice cold alcohol
4. DNA comes out of solution as its not soluble in cold alcohol
   a) a stringy white precipitate (solid), fish out with glass rod

Question 5

Explain why there are differences in the inherited characteristics
as a result of alleles

Answer 5

• dominant alleles beat recessive alleles
• dominant alleles chose which characteristics are present
• differences in characteristics are caused by 2 recessive alleles

Question 6

explain the term chromosomes

Answer 6

coiled up molecules of DNA, found in nucleus of eukaryotic cells

Question 7

explain term allele

Answer 7

different versions of genes

Question 8

explain term dominant

Answer 8

-capital letters
-always expresses itself even with recessive

Question 9

explain term recessive

Answer 9

-lower case
-supressed in presence of dominant

Question 10

explain term homozygous

Answer 10

same alleles

Question 11

explain term heterozygous

Answer 11

different alleles

Question 12

explain term genotype

Answer 12

genetic information

Question 13

explain term phenotype

Answer 13

physical feature

Question 14

explain term gamete

Answer 14

sex cells, sperm and egg

Question 15

explain term zygote

Answer 15

fertilised egg
- when a male gamete fuses with female gamete to produce a fertilised egg

Question 16

what is monohybrid inheritance

Answer 16

inheritance of a single characteristic

Question 17

Describe how the sex of offspring is determined at fertilisation

Answer 17

• girls have XX, boys have XY (Y causes male characteristic)
• eggs, one X chromosome
• sperm, either X or Y chromosome
• so equal chance of boy or girl
  — sex determination depends on the sperm that fertilises egg carries and X or Y chromosome

Question 18

what are most phenotypic features a result of

Answer 18

multiple genes not single gene inheritance
- different combinations of alleles give different phenotypes

Question 19

describe causes of variation that influence the phenotype

Answer 19

a) genetic variation - organisms have different alleles, different characteristics as a result of mutation and sexual reproduction - > difference in phenotype

b) environmental variation - different characteristics cause by an organisms environment (acquired characteristic), characteristics an organism gets in life

Question 20

Discuss the outcomes of the Human Genome Project and its
potential applications within medicine

Answer 20

the HGP wanted to find all human genes
- genes help predict diseases they might get
a) helps predict and prevent diseases - get advice to stop disease
b) testing and treatment for inherited disorders - faulty alleles, identify disorder quick to get better treatment
c) new and better medicine - shows genetic variations, can design new drugs tailored to people with particular genetic variation, shows how well existing drug works (how people respond to it too), how the disease affects us to understand it and develop more effective treatments

• downsides= stress, geneism, discrimination

Question 21

State that there is usually extensive genetic variation within a
population of a species and that these arise through mutations

Answer 21

-mutations are changes to base sequence of DNA
- mutations are the main source of genetic variation
- when in a gene, results in allele or different version of gene

Question 22

how badly do genetic mutations effect people

Answer 22

• most have no effect on phenotype
• some have small effect of phenotype
• rarely a single mutation will hugely affect phenotype