Human Genetics MT 3 pt 2

tRNA

• translates genetic code

• delivers correct amino acid to mRNA

genetic code

• used by all organisms

• 3 bases read at a time

• encodes for one amino acid

• read from start to stop codon

can several codes have the same meaning in the genetic code?

yes, called degenerate

what is the start codon?

• signals ribosome to start translation

• methionine—>AUG

stop codon

signals ribosome to stop translation

inititation

transcription factors and RNA polymerase bind to promoter

promoter

DNA sequence that signals start of a gene

elongation

• enzymes unwind DNA double helix

• RNA nucleotides bond with bases

• RNA polymerase adds RNA nucleotides

termination

when terminator sequence in DNA is reached and encoding ends

can only one protein be made from a single mRNA?

no, many proteins can be made

denaturing

when protein changes shape and loses its function

chaperone proteins

helps fold and stabilizes proteins

what does the shape of a protein relate to?

its function

what can cause long term effects in fetal development?

fetal environment

transcription factors

helps or hinders RNA polymerase binding to promoter

what triggers transcription factors?

• signaling molecules

• ex. hormones

steroid hormones

• regulate transcription factors by activating them

• ex. estrogen, testosterone

chromatin remodeling

• changing how tightly chromatin is packed around histones

• makes promoter more accessible

is DNA positively or negatively charged?

negatively charged

histone modification

• chemical changes to protein that alter how tightly DNA is wrapped around them

• gene not expressed if promoter is tightly wound

• reversible, does not change DNA

acetylation

• reduces positive charge of histones

• results in less compact DNA

• promoter becomes more accessible

methylation

• addition to methyl group to cytosine base in DNA

• turns genes off

• decreases transcription

alternative splicing

• occurs in pre-mRNA

• combines exons in different ways

• use one gene to make multiple proteins

post transcriptional control

• allows cells to be transcribed but not translated

• regulates gene expression after transcription

• ex. poly-A tail, microRNA

microRNA

• small RNAs that bind to mRNA

• block translation

In Which Type Of Cells Would You Expect Sex Steroids To Be Able To Behave As Transcription Factors To Turn On Genes?

cells with androgen receptors

anabolic steroids

• synthetic forms of androgens

• signaling molecules

negative feedback (testosterone)

body senses high levels of testosterone and signals to stop making it

cortisol

stress hormone

glucocorticoid receptor protein (GRP)

helps shut down stress response

lick your rats activity

• pup raised by anxious, low-nurturing mother becomes anxious adult

• pup raised by relaxes, high-nurturing mother becomes relaxed adult

methylation and GRP levels in high vs low natured rats

• high nurtured: low methylation, high GRP expression (quickly recover from stress)

• low nurtured: high methylation, low GRP expression (slowly recover from stress)