Genetics Flashcards
(20 cards)
What is a gene?
A section of DNA that codes for a protein.
How many chromosomes do humans have?
46 (23 pairs).
What is a karyotype?
A picture of someone’s chromosomes.
What are alleles?
Different versions of a gene.
What is the difference between genotype and phenotype?
Genotype: genetic makeup. Phenotype: physical traits.
What does dominant mean in genetics?
The trait is seen if at least one copy is present.
What is recessive inheritance?
The trait is only seen if both copies of the gene are the same.
What is codominance?
Both alleles are expressed (e.g., AB blood type).
What is an example of a sex-linked disorder?
Colour blindness, haemophilia.
What is trisomy 21?
Down’s syndrome.
What is a point mutation?
A change in one base of DNA.
What causes cystic fibrosis?
A mutation in a gene that makes a chloride channel.
What is the role of BRCA1?
A gene that helps prevent cancer.
How does genetic variation happen?
Independent assortment, crossing over, random fertilisation.
What is polygenic inheritance?
Many genes contribute to a trait (e.g., height).
What is a pedigree chart used for?
To trace inheritance of traits through generations.
What are carrier screening tests for?
Identifying people with a gene for a recessive disorder (e.g., CF).
What is preimplantation genetic testing?
Testing embryos before implantation in IVF.
How is prenatal genetic testing done?
Amniocentesis or chorionic villus sampling.
What is the chance of having a child with CF if both parents are carriers?
0.25
