Genetic disorders and diagrams Flashcards
Who was Gregor Mendel? What did he research?
The founder of genetics. How characteristics in plants were passed on from generations.
What plant did Mendel use to show his theory?
Pea plants
What did Mendel show with the pea plants? (Genetic theory)
Character
Who from
Ratio, t
The height characteristic in pea plants was determined by separately inherited” hereditary units” passed on from each parent.
The ratios of tall and dwarf plants showed that the unit for tall plants, T was dominant of the unit for dwarf , t.
What were Mendel’s three important conclusions about hereditary in plants?
Characteristics
Parent
Dominant
characteristics in plants are determined by “hereditary units”
hereditary units are passed down from both parents, one unit each
hereditary units can be recessive or dominant
If an organism has both a recessive and dominant unit, which characteristic will be expressed?
The dominant characteristic.
What are hereditary units? Why didn’t Mendel know about them?
Genes, DNA and genes had not been discovered yet.
What do genetic diagrams show?
The possible genes of an offspring.
What are alleles? In genetic diagrams what are used to show these?
Different versions of the same gene. Letters.
If an organism has two alleles for a particular gene it’s ….zygous
HOMOzygous
If an organism has two different alleles for a particular gene it’s ….zygous
If two alleles are different only one can determine the characteristic.
HETROzygous
The allele for the characteristic that is shown is called the …, shown with a …. letter. The other is a …. shown with a … letter.
DOMINANT, capital
RECESSIVE, lower case
For an organism to display a recessive characteristic what type of alleles must it have?
Two recessive.
What two combinations of alleles allow an organism to take on the dominant allele characteristic?
DD, or Dd, Two dominants (homo) or hetro … dominant and recessive.
What does genotype mean?
Where does this sit on a genetic diagram?
What alleles you have.
The parent’s have genotypes, along with the Gametes and offspring.
What is a phenotype?
Where does this sit on a genetic diagram?
The actual characteristic the organism has.
At the top and the bottom, showing what the parents are like, Crazy/ normal, then what the children are like… one crazy, two normal.
What is it called when you cross two parents to look at just one characteristic?
Monohybrid cross
What types of alleles cause cystic fibrosis?
Two recessive alleles.
What is the affect on the body caused by the inherited disorder, cystic fibrosis?
The disorder is of the membrane of cells, they produce a lot of thick sticky mucus in the air passages and in the pancreas.
How many people carry the cystic fibrosis allele?
1/25
What do you call a person with only one allele for the disorder?
A carrier, with only one copy of the allele, it’s recessive so they don’t suffer.
What must the parents’ alleles be if a child has the cystic fibrosis disorder? What chance is there of inheritance then?
Both carriers or sufferers. 1/4
What type of alleles is Polydactyly caused by?
At least on dominant, e.g Dd dd
What is polydactyly?
A genetic disorder where a baby’s born with extra fingers or toes, not usually causing other problems so not life threatening.
What is polydactyly caused by? What does this mean for the parent? What are the chances of inheriting the disease?
A dominant allele, at least one parent must be a sufferer of this disease.
50%
What does IVF involve that’s controversial?
Screening for disorders
What happens during IVF?
Embryos are fetilised in the lab then implanted into the mother’s womb, usually more than one to maximise chances of success
What happens in IVF to screen the embryos?
Before implantation one cell is removed and they analyse its genes for many genetic disorders such as cystic fibrosis. Good alleles - embryos are implanted, the others are destroyed.
What are four reasons against embryonic screening? Desire Life Prejudice Money
There may come a point where everyone wants their embryos screened so they can have the most desirable characteristics for their offspring.
The other embryos are destroyed and could have been a human later.
It implies people with genetic problems are undesirable, increasing prejudice against them.
The screening is expensive.
What are four reasons for embryonic screening? Law Suffer Ensure Money
There are laws to stop screening going too far, parents can only select the sex of their baby for health reasons and risk.
It will help to stop suffering in the born child
The embryos would be destroyed anyway if not used, but screening ensures the baby born will be the healthiest one.
Treating and caring for the disorders costs the government a lot of money.
if one parent has one (the only) recessive allele, how many children will carry the disorder?
None
If one parent has two recessive alleles for a disorder and the other parent has two dominant, what % will have the disorder? (DD dd)
None.
if one parent has one (the only) dominant allele, how many children will carry the disorder?
Two
If a baby’s parents are both Dd, what are the chance it’ll be a carrier or a sufferer? Where d is recessive and causes the disorder.
25% of sufferer, 50% of carrier. (Draw a grid D d on the top row then
D
d
on the side column and show the alleles int their pairs to work it out.
What is an allele?
A type of gene
What does recessive mean?
Only expressed if two copies are inherited.
Individuals who are homozygous for a certain gene carry how many copies of it?
two copies of the same allele
Individuals who are hetrozygous for a certain gene carry how many copies of it?
two different alleles
