Variation and Inheritance quiz

the slideshow + the lab

Variation is controlled by…

genes and environment

Types of variation

Continuous variation (like height)

* Controlled by many genes plus the environment
* Difficult to study

Discontiuous variation (like the ability to roll your tongue)

* Sometimes controlled by a single gene
* Much easier to study

Genetic sources of variation

Mutation

* ^^Gene mutation^^ (a change of base sequences within a gene, ex. sickle cell anemia)
* ^^Chromosome mutation^^ (a change to the number of chromosomes, ex Down’s syndrome)

Meiosis

* ^^Remixes genes^^ to create variation

Cell division and meiosis

Cell division occurs ^^twice with meiosis^^, so you put numbers after the phases (ex. telophase II)

During prophase I the chromosomes are ^^crossing over^^, and ^^exchanging genetic information^^. During prophase II this does not happen, because there are no longer any pairs similar enough to trade info with.

Homologous chromosomes

Chromosomes that have the ^^same size and structure^^, as well as the ^^same genes^^ in the same sequence (twins!)

Homologous chromosomes can pair up and trade information with each other

Gene

A code for a characteristic

Allele

A version of a gene

Homozygous

Both alleles are the same in the genotype (“pure” genes)

Heterozygous

The alleles are different in the genotype

Dominant allele

An allele that is always expressed in the phenotype (always shows)

Recessive allele

An allele that is only expressed in the homozygous state

Codominant alleles

Alleles that are equally expressed in the phenotype

Genotype

The pair of alleles of an individual

Phenotype

The characteristics or traits

Genome

All the genetic information of an individual or species

How to write alleles

Dominant alleles are written with a capital letter (ex. B for brown eyes) and recessive alleles with a small letter (ex. b for blue eyes). Codominant alleles are written with superscript (ex. CR for red flowers and CW for white flowers)

Gregor Mendel’s experiment on purple and white flowers

Purple + White (gen 0) → All purple (gen 1) → 75% purple and 25% white (gen 2)

So purple must be the dominant allele

Sex-linked genes

Sex-linked genes appear on the ^^X-chromosome, but not on the Y^^. This means that people with XY chrommosomes are more likely to be affected by this type of gene, since they only need ^^one copy of the gene to be affected^^.

Ex. red-green colour blindness and haemophilia are sex-linked.

Pleiotropy

One gene affects two or more characteristics

Polygenes

Two or more genes affect one characteristic

GWAS

Checking for high (or low) frequency of a certain gene (SNPs or snips) within a group compared to the general population, to find genes that likely cause the trait that the group has.

Why do we want to know which genes do what?

Well, if you know the ^^base sequence^^ that is (probably) involved in causing a disease

Then you know what ^^amino acid sequence^^ is made, and the ^^shape of the protein molecule^^

Chemists can then investigate the ^^properties of this protein^^ molecule

Medics can ^^look for this protein molecule in people^^ with the disease

Cell Biologists can ^^grow cells and add, or remove, this protein^^ molecule to see what the effects are

Doctors then might be able to ^^relate this to symptoms in people with the disease^^, and be able to ^^test treatments^^ on volunteers

And hopefully the disease can be ^^treated better or even cured^^

Enzyme lab!

Heat speeds up reactions, so the reaction was much quicker in the warmer water baths. However, this is only true up to a certain point, because in too high temperatures the enzymes start denaturing, which will slow down the process, or even stop it completely.