Topic 3 Genetics

Question 1

What is meiosis?

Answer 1

• four daughter cells
• half the number of chromosomes
• formation of genetically different haploid gametes

Question 2

What is DNA?

Answer 2

DNA( deoxyribonucleic acid) is the genetic material found in the chromosomes in the nuclei of cells.
- two strands coiled to form a double helix
- stands linked by a series of complementary base pairs joined together by weak hydrogen bonds
- nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar
- A-T C-G

Question 3

Genetic terms

Answer 3

Gene- short piece of DNA at a particular point on a chromosome
Allele- produce different variations of the characteristics
Heterozygous- different alleles of the same gene
Homozygous- the genes have the same allele on both chromosomes
Phenotype- the characteristics are produced including what an individual looks like
Genotype- shows the alleles in the individual
Dominant- one copy is present in the genotype
Recessive- two copies is present in the genotype
Zygote- a fertilised egg cell
Gamete- reproductive cell in an animal or plant

Question 4

How do extract DNA from fruit?

Answer 4

• grind the fruit with sand, using a pestle and mortar to separate the cells
• adding a detergent to break open the membranes
• adding ice-cold alcohol so that the DNA precipitates out

Question 5

What is monohybrid inheritance?

Answer 5

Monohybrid inheritance can be explained using genetic diagrams and punnet squares.
- a punnet square shows the same information about how genotypes is inherited and what effect this has on the phenotype
- genetic diagrams shows possible offspring

Question 6

What are family pedigrees?

Answer 6

You can use a family pedigree to show the inheritance of a genetic condition within a family, and to predict the chance that someone will inherit the faulty allele.

Question 7

What is inherited characteristics?

Answer 7

An inherited characteristic is controlled by a single gene that has multiple alleles. The sex chromosomes x and y are not a matching pair. Males only have one X chromosome. A recessive allele on this chromosome will affect the phenotype as it is not matched by a dominant allele on the Y chromosome.

Question 8

What is variation and mutation?

Answer 8

Causes of variation that influence phenotype include genetic variation and environmental variation. Genetic variation happens through mutation.
Variation- caused by a combination of genes and environment
Examples: skin colour, weight and maybe how to ride a bike
Mutation- the sequence of bases in a gene is changed
Examples: a large change in protein produced or a small change in protein produced

Question 9

What is the human genome project?

Answer 9

The human genome project is collaboration between scientists to decode the human genome. The results are being used to develop new medicines and treatments for diseases.
Advantages:
- allows doctors to tailor treatments
- alerts people that they are at a particular risk of certain diseases
Disadvantages:
- people might have to pay more to obtain life insurance
- it may not be helpful to tell someone they are at risk of a condition that there is no cure for

Question 10

What is the genome?

Answer 10

The entire DNA of an organism and a gene as a section of a DNA molecule that codes for a specific protein

Question 11

What is genetic and environmental variation?

Answer 11

Genetic variation- different characteristics as a result of mutation and sexual reproduction
Environmental variation- different characteristics caused by an organisms environment