Topic 6b- Genetics Flashcards
What are the male chromosomes?
XY
What are the female chromosomes?
XX
What are the chances that a baby is male / female?
50 / 50
How many alleles do normal cells in an organism have?
2
How many alleles do gametes have?
1
What does homozygous mean?
If an organism has two alleles for a particular gene that are the same
What is it called when an organism has two alleles for a particular gene that are the same
Homozygous
What does heterozygous mean?
When an organisms two alleles for a particular gene are different
What is the allele that is shown called?
The dominant allele
What is the allele that doesn’t show up?
recessive
What is a genotype?
The combination of alleles that an organism has
What is a person’s phenotype?
The physical characteristics that are displayed due to their genotype
What is single gene inheritence?
One gene is inherited from the father and one gene is inherited from the mother (it’s just a fance word for basically normal inheritence)
What are the two inherited disorders you need to know at GCSE?
cystic fibrosis and polydactyly
What is cystic fibrosis?
An inherited disorder of cell membranes resulting in the body producing lots of thick mucus in the air passages and in the pancreas
Is the allele that causes cystic fibrosis dominant or recessive?
recessive
What are carriers (in reference to genetic disorders e.g. cystic fibrosis)
people with only one copy of the allele (therefore they are heterozygous) meaning that they have no symptoms
What is polydactyly?
An inherited disorder where someone’s born with extra fingers or toes
Is the allele for polydactyly dominant or recessive?
dominant
What is a family tree in genetics?
A diagram that shows how a characteristic (or disorder) is inherited in a group of related people.
What is embyronic screening?
A way of detecting disorders such as cystic fibrosis in embryos
In what was can embryonic screening be done? How do they work?
- Pre-implantation genetic diagnosis (PGD) - During IVF the cells in an embryo can be removed and analysed, therefore embryos with ‘healthy’ alleles could then be implanted into the mother while the others destroyed.
- Chronic villus sampling (CVS) - Usually carried out between 10-13 weeks of pregnancy CVS involves taking a sample from part of the placenta and analysing their genes (since the placenta develops from the same original cell and therefore genes as the embryo) after analysis the parents can decide whether or not to terminate the pregnancy