Gene Expression and Mutations in Honors Biology

Mrs. Werner's Honors Biology 10 class - Punnett squares -

What was the Blending Theory?

This is the first(now disproven theory) of Genetic Inheritance

Each trait only had one chromosome. After fertilization, both your parent’s DNA/traits mixed together to create on e new DNA/trait in you.

Ex: Mom’s short and Dad’s tall traits mixed and you came out medium height, you can only then pass on medium height

What was a major issue with the Blending Theory?

When grandkids would come out too short or too tall, this theory couldn’t explain the traits that “skipped traits”

Who was Gregor Mendel

-Gardening monk, very dedicated, prayed 12 times a day

-One of the first scientists to truly study genetics and used his pea plants AS TEST SUBJECTS

-It is thought that he was autistic, but he could see complex math and science in his head like it was nothing

-He had millions and millions of pea plants, and he would pluck them, shuck them, planting, and storing peas because he had a lot of time at the monestary

-Known as the Father of Genetics

-Created the 3 basic principles that began modern genetics which is the study of heredity - the passing of traits from parent to offspring

What are the principles of Dominance and Recessiveness

2 different chromosomes for every trait and therefore 2 possible alleles

Dominant - A strongly expressed gene that shows up. Seen as the Capital letter (ex: B)

Recessive - allele which is either caused to be not seen due tot he dominant gene or is weakly expressed. Seen as the smaller case letter (ex: b)

-Blond is recessive to brown hair

-White flowers is recessive to Purple flowers

What are alleles?

A trait is made of 2 or more alleles

-Homozygous - having all the same type of allele

• Homozygous dominant (BB)

• Homozygous recessive (bb)

-Heterozygous - having a variety of same type of alleles (Bb)

What is the Principle of Segregation?

During sexual reproduction ( when making the sperm or the egg) only 1 of the parent’s allele is passed on per gamete made

• Dad is heterozygous for Brown Hair (Bb). When making his sperm, his chromosomes will segregate randomly during anappase of meiosis

  • segregation - move to opposite sides of the cell

• Now dad has a sperm with

  • Blonde traits (b)

  • Brown traits (B)

What is the Principle of Independent Assortment?

Organisms have many sets of chromosomes that are sorted during meiosis. HWne traits are passed on they can be on different chromosomes which get pulled to opposite ends of a cell RANDOMLY during Anaphase 1

EACH chromosome then can be said to RANDOMLY and INDEPENDENTLY sorted from each other. The only “rule” is that ONE of each of the same chromosomes gets moved to each gamete

So, each trait has teh same chance of being given to the child from that parent’s gamete

What is Probability?

The likelihood of something happening, can be expressed as a ratio or a percent

Ex: flipping a coin; what are the 2 possible outcomes?

• heads or tails

Now what is the possibilty of getting heads?

• 1:2 or 50% chance of flipping heads

What is the chance of flipping 4 heads in a row?

• 1/2×1/2×1/2×1/2 = 1/16

What are Punnett Squares?

Tools used by geneticists to help determine gametes and possible offspring

What are the types of Inheritance/ Genetic Mechanisms?

Simple/Complete Dominance

Codominance

Intermediate/Incomplete Dominance

What is SImple or Complete dominance?

Where you have 2 alleles: a dominant and recessive where the dominant covers the recessive

What is Codominance or Intermediate/Incomplete dominance?

You must write these alleles as a Capital letter(describing the trait) and a Capital superscript (describing teh specific phenotype) like F=Flower, superscript R for Red.

Ex: F^R would now be the allele

Co-Dominance

2 alleles, both dominant that will show and NOT mix the phenotypes together when both are present (heterozygous) but instead both show up, like stripes or spots.

Intermediate/Incomplete Dominance

2 alleles, both dominant that will show and mix teh phenotypes together when both are present, ex mixing red and white making pink.

Multiple alleles

Has a recessive and 2+ dominant alleles

It creates a wider variety of trait combinations

Polygenic traits

Where 2+ more genes create one trait

• Skin color has 4 allele pairs that code for it

• this creates variations in traits like shades, colors, lengths, etc.

Epistasis

A gene that stops teh expression of another gene

• The strawberry tint to hair can’t happen if the hair is too dark

What are environmental effects on genes?

Tempereature, amount of light, and amount of nutrients can also effec tthe way a gene works

What is Sex-Linked inheritance

• can follow any of the previously mentioned genetic inheritance patterns

• are only carrried on teh sex (X & Y) chromosomes

• usually diagnosed when only 1 type of sex consistently has the trait

What is a Frame Shift Mutation

It is an error in Translation when there are errors in reading the DNA/RNA

• Addition

• Deletion

Both examples of frameshift mutation

Has the most effect on the DNA strand

What is Point Mutation?

Where a specific nucleotide is edited in a DNA sequence

What is Deletion ?

Frameshift mutation, big effect on DNA sequence

• Some nucleotide(s) were removed (like during splicing or transcription) so there is now an incorrect sequence

Insertion

Frameshift mutation, big effect on DNA sequence

• Random additional nucleotides or RNA pieces(like introns) are added during splicing or trsanscription

What is substitution?

Point Mutation, NOT a frameshift, sometimes considered a silent mutation if it has no effect on the amino acid

• A different or incorrectly matched nucleotide is placed where another should be

What is Translocation?

Chromosomal Mutation, not a frameshift, still just a regular point mutation

• Occurs whena piece of one chromosome breaks off and attaches to another chromosome

What is an Inversion Mutation?

Part of the chromosome is broken off and flipped before reinserted

What are silent mutations

have no effect on teh amino acid produced by a codon becuase of the redundancy in the genetic code

What are missense mutations

still code for an amino acid, but not necessarily the right amino acid,

creates junk

what is a nonsense mutations

changes an amino acid codon into a stop codon, nearly always leading to a nonfunctional protien