Chapter 8- modern genetics Flashcards
Most traits are a result of
Complex patterns of inheritance
Incomplete dominance
One allele is only partially dominant (mixing of traits - ex. snapdragons)
Codominant alleles
Both alleles show equally (ex. speckled chicken)
Multiple alleles
Three or more possible alleles determine a trait
An organism can only inherit _______ alleles for a gene (one from each parent)
Two
Polygenic inheritance
Occurs when more than one gene affects a trait (ex. human skin and height)
How many pairs of chromosomes do humans have?
23
- first 22 are called autosomes
- 23rd is sex chromosome
Sex chromosomes (male vs. female)
Female: XX
Male: XY
Sex-linked traits
Traits controlled by genes on sex chromosomes (ex. colorblindness)
The order of the nitrogen bases along a gene form a ______________ that specifies what type of protein will be produced
Genetic code
Proteins are what
Long chain molecules made of amino acids
What is a group of three bases called
A codon
What does a codon code for
One specific amino acid
How many amino acids are there in the human body
20
Protein synthesis
Amino acids link to form proteins
Where does protein synthesis begin
Inside the nucleus
Where does assembly of proteins occur
Outside the nucleus on ribosomes
In what ways is RNA different form DNA
- RNA contains the sugar ribose instead of deoxyribose
- RNA does not have thymine instead it has uracil
- RNA is single-stranded
mRNA
carries copies of instructions for the assembly of amino acids into proteins from DNA to ribosomes in the cytoplasm (this is called transcription)
tRNA
Translates these instructions into amino acids and carries them to the ribosomes during protein synthesis (this is called translation)
Mutations
Any change in a gene or chromosome (can be inherited or acquired during life)
Inherited mutations
- parent passes on mutation during reproduction
- present in every cell of the body
- present through the life of an organism
Acquired mutations
- occur during an organism’s life
- can only be passed to offspring if mutation occurs in sex cells
What can one small change to a base pair cause
An incorrect protein to be made during protein synthesis
