W20 L1 - Genetics and Evolution Lecture Notes

Flashcards about genetics, dominant and recessive genes.

If there is a big scandal where horse meat is being sold in Tesco's frozen lasagna instead of cow meat, how do you test this?

To test if frozen lasagna contains horse DNA instead of cow DNA, you need to design PCR primers that will amplify horse DNA but not amplify cow DNA.

You are selling a sausage as extremely expensive wild boar rather than pig. How do you design a primer to tell if this is a real thing?

To tell if a sausage is from a normal pig or a wild boar, you need to design primers to tell the difference between their DNA.

How do you design primates to detect a large deletion within the genome?

If a person has a mutation in their genome that causes their cell to become cancerous, you can design a PCR that will detect the deletion bits of DNA.

What is the second half of the practical write up asking you to do?

It is asking you to use your molecular biology knowledge to interpret the results of a PCR experiment which is designed based on what we do when we talk through the computer practical tomorrow which is the actually running design of some PCR practicals.

What are simple single gene disorders?

A single gene in the genome, which when mutated, is causative for a given disease.

What are examples of Mendelian conditions where you have a simple causative pathway from genotype to phenotype?

Sickle cell anemia is caused by a specific mutation within the hemoglobin gene. Cystic Fibrosis can be caused by actually quite a large number of different mutations but any mutation that impairs the function of the CFTR.

How do you spot an autosomal dominant disorder?

Whenever I give you a pedigree, look at it and say, who is affected? If so, think autosomal rather than sex linked. Are you seeing transmission from father to son, and father to daughter.

In Autosomal Resetive Disorders, are men and women equally affected?

Men and women equally affected because it's an Autosomal Disease. And you see transmission transmission from father to son, father to daughter, mother to son, mother to daughter, all of those can happen.

If you see a pedigree where predominantly men are being affected, what should you immediately start thinking?

If you see pedigree where predominantly men are being affected, you should immediately start thinking this may be sex linked. This may be an X linked recessive disorder because the man only has one X chromosome and therefore all his recessive alleles get exposed and all the recessive traits get revealed in men whereas women can carry it.

In what type of disease pedigree, are the women always passing it on and the men are never passing it on?

Only the women are always passing it on and the men are never passing it on because only the mother passes mitochondria to that zygote in the egg because the DNA that's not within the nucleus, it's the DNA that's in the mitochondria in the cytoplasm of the cell.

What is a genetic disease?

A disease that is linked to mutations in the in in genes that is to be inherited in some form.

What are mutations?

Variations in genetics. Something where different people in the population have different genetic variants.

What does it mean if variations affect the ability to reproduce?

We know that some variations affect the ability to reproduce. And that will, is what shows up as evolutionary fitness.

How do medical professions define disease?

Is it causing somebody to suffer a phenotype that they rather not have?

In sickle cell anemia, why are heterozygotes protected from malaria?

The heterozygotes are somewhat protected from malaria. And in that case, you're selecting for the presence of the sickle cell anemia allele because it helps protect against malaria.

What does Dominant otosclerosis cause?

The bones of the ear to become hardened, stuck together causing basically hereditary deafness.

For a dominant disease, how can you think of the frequency of affected alleles?

Think of the frequency of affected alleles as q. Which means the frequency of wild type alleles, healthy alleles will be one minus q, p.

What plays into the prevalence of different diseases in the populations?

The mutation rate and the selection rate both play into the prevalence of different diseases in the populations.

How do de novo mutations arise?

As we pass genes from one generation to the next, occasionally, something will be copied wrong.

What is the concept of mutation selection balance?

How readily are new allele, causes of allele are generated relative to the rate at which they're removed from gene pool by selection.

If I ask you to write an essay on why are some genetic diseases more common than others, what concepts do I want you to talk about?

Mutation selection balance. I want you to talk about the mutation rate. How easily mutations happen. I want you to talk about selection. How efficient selection is at removing those alleles.

When will Individuals only be selectively disowarded?

If it affects reproductive capacity.

What causes triplet repeat disorders such as Huntington's Disease?

CAG, CAG, CAG repeated one after the other. These are unstable when being copied.

Why are triplet repeat disorders more common to the paternal line?

It's more common to the paternal line because you have many more cell divisions involved in producing a sperm than an egg, which means anticipation of particular common path from father to son.

In triplet repeat disorders, what happens when they are passed from one generation to another?

Triplet repeat tend to expand over time.

What might be causing the severity of the disease to increase from generation to generation?

Areas in replication of DNA leading to the mutation become more severe over time.