B14- Genetics Flashcards
What is DNA made of
made up of two strands forming a double helix.
What is a gene
A gene is a small section of a chromosome that codes for a particular sequence of amino acids, to make a specific protein.
How many chromosomes do humans have (pairs)
23 pairs of chromosomes
46 chromosomes
What are alleles
Each gene may have different forms called alleles.
What are the 2 formes of alleles
recessive
dominant
What is meiosis
Meiosis is a type of cell division that occurs in the testicles or ovaries to produce non-genetically identical sex cells/gametes (sperm or egg cells).
What are the stages of meiosis
1) DNA replicates
2) The cell divides twice to form 4 genetically non identical gametes (sex cells)
3) Each gamete contains a single set of chromosomes (23 chromosomes in a human).
Why do Scientists study the genome?
They can search for genes linked to different types of disease
To help them understand and treat inherited disorders
Use what they find in tracing human migration patterns from the past.
What is a Chromosome
A chromosome is a long coiled structure composed of DNA and protein.
What are Dominant allele
An allele that is expressed (even if there is only one dominant allele)
What are Recessive allele
An allele that is ‘masked’ by a dominant allele. Recessive alleles are only expressed if they occur in pairs
What does Homozygous mean
Genotype where an individual has two identical alleles for a specific gene
What does Heterozygous mean
Genotype where an individual has 2 different alleles for a specific gene
What is the meaning of Phenotype
The physical expression of one’s genotype due to its interaction with the environment
What is the meaning of Genotype
The genetic constitution of an organism
What is the meaning of Gamete
Is a sex cell, that contains half the number of chromosomes than a normal body cell
What is an Example of a dominant disorder
Polydactyly (having extra fingers or toes) is caused by a dominant allele.
What is an Example of a recessive disorder
Cystic fibrosis (a disorder of cell membranes) is caused by a recessive allele.
What is the advantages of genetic screening
The parents can decide whether or not to have the baby and continue with the pregnancy
They will know if there is a possibility of getting ill in the future
Preparation- the family or the person can plan ahead and could get treatment for the condition
What are the disadvantages of genetic screening
Risk of miscarriage/ harm to the mother or the foetus
Test might not be reliable
Screening is very expensive
Wrong in some religions
