B6 - Inheritance, Variation and Evolution Flashcards
What is DNA
The genetic material in the nucleus of a cell is composed of a
chemical and is a polymer made of two strands to form a double helix
What is a gene
A gene is a small section of DNA on a chromosome
What does each gene do
Each gene codes for a particular sequence of amino acids, to make a specific proteins
What is a genome
Entire set of genetic material in an organism
Why is understanding the human genome important (3 marks)
search for genes linked to different types of disease
understanding and treatment of inherited disorders
use in tracing human migration patterns from the past.
What is sexual reproduction
genetic information from two organisms are combined to produce offspring which are genetically different to either parent
In sexual reproduction how does the mother and father produce gametes
meiosis
What is asexual reproduction
One parent - no fusion of gametes - no mixing of genetic information - genetically identical offspring through mitosis
Give two examples of sexual reproduction
sperm and egg cells in animals
* pollen and egg cells in flowering plants.
What happens when a cell divides to form gametes (3 marks)
copies of the genetic information are made
* the cell divides twice to form four gametes, each with a single set of chromosomes
* all gametes are genetically different from each other
Describe what happens from gametes meeting at fertilization to the embryo’s cell(4 marks)
Gametes join at fertilization to restore the normal number of
chromosomes. The new cell divides by mitosis. The number of cells increases. As the embryo develops cells differentiate to make up an organism
How many times does the cell divide and how many cells are produced
(meiosis)
2
4
What does allele, phenotype and genotype mean
Allele: Different versions of a gene
Genotype: combination of alleles
Phenotype: Characteristic determined by alleles
Give an example of homozygous recessive/dominant and heterozygous
(using b’s)
Homo.R - bb
Homo.D - BB
Hetero- Bb
Phenotype/Genotype for Polydactyly
Phenotype - extra toes or fingers
Genotype - dominant allele
Phenotype/Genotype for Cystic fibrosis
Phenotype - body producing excess amounts of mucus
Genotype - recessive allele
For and against arguments for embryonic screening (6 marks)
For:
Help stop people from suffering
Treating disorders cost the government a lot of money
There are laws to stop it going too far i.e. parents can not select the sex of their baby unless for health reasons
Against:
Implies that people with genetic problems are ‘undesirable’ - could increase prejudice
Many come to a point where everyone wants to screen their embryos for more desirable phenotypes
Screening is expensive
