Genetics Quiz 4

nucleus

DNA is stored in the ___

cytoplasm

Protein is made in the ___

Carbohydrates, lipids, proteins, and nucleic acids.

What are the biological molecules?

polymer

a chain of amino acids linked by peptide bonds

polypeptide

a specific type of polymer

3D structure

Amino acids fold into a _____ ______ based on their amino acid sequence. (Important for protein function).

general structure

all amino acids have the same _____ ______

R group

• It is different in each amino acid.

• It can be an uncharged, positive, negative, or aromatic ring.

An amino-terminal end and a carboxyl-terminal end

proteins have……

Primary Structure 1

• linear sequence of amino acids in a polypeptide chain

• covalent bonds

Secondary structure 2

• interactions between nearby amino acids

• hydrogen bonds

tertiary structure 3

• 3D shape of protein

Quaternary structure 4

• interactions between multiple polypeptide chains

protein structures

Primary, Secondary, Tertiary, and Quaternary.

structural support

Collagen, and keratin in connective tissue.

signalling

Hormones (insulin) work as chemical messengers

transport

hemoglobin transports oxygen in blood

defense

antibodies

cellular processes

Enzymes make DNA, RNA; function in biochemical pathways to make carbohydrates and lipids.

mRNA

• “messenger“

• proteins are made by ribosomes in cytoplasm

transcription

• DNA —> RNA

translation

RNA —> protein

• mRNA is read 5’ —> 3’

• mRNA is read in the cytoplasm

• mRNA is read by the ribosome

phenotypes

______ arise because of the synthesis of specific proteins.

DNA

• deoxyribose

• A, G, C, T

• double-stranded

RNA

• ribose

• A, G, C, U

• single-stranded

messenger RNA function

• carries genetic information from nucleus to the cytoplasm

ribosomal RNA function

• part of protein synthesis machinery (ribosome)

transfer RNA function

• carries amino acids to ribosome

complementary

Sequence of new RNA is _____ to DNA template

functional molecules

Only DNA sequences that code for _____ will be transcribed.

What cells need for transcription

• cellular machinery that makes RNA (nucleic acid polymer) - a protein called RNA polymerase

• building blocks (monomers) that join together to make poly - ATP, GTP, UTP, and CTP

• instructions (the DNA template) - only ONE STRAND of double-stranded DNA

monomers

small, simple building blocks that combine to form larger, more complex molecules called polymers

How the template strand is chosen

Promoter

• DNA sequence right next to a gene

• provides a binding site for RNA polymerase

• always on the 5’ side of a gene (“upstream“)

• tells RNA Polymerase where to start making mRNA

antiparallel

RNA polymerase works (makes new mRNA) 5’ —> 3’ ALWAYS so it will read DNA strand that is ______

3 steps of transcription

1. initiation

   - RNA polymerase binds to DNA at the promoter

   - DNA is “melted”

   - the process begins

2. elongation

3. termination

   - RNA polymerase releases DNA and RNA

   - caused by DNA sequences at the 3’ end of the gene

RNA is made 5’ —> 3’

eukaryotes

in ______, mRNAs are “processed“ before they leave the nucleus

5’ capping

5’ end of mRNA is chemically modified

3’ polyA tail formation

3’ end of mRNA is extended by the addition of many adenine nucleotides

intervening sequence and expressed sequence

Intron sequences are removed; exons are spliced together

1st is not translated

2nd is translated

processing events to create a mature mRNA

1. cap added to 5’ end

2. poly-A tail added to 3’ end

   - # of A nucleotides tells the age of mRNA

   - polyA tail shortens over time

   - when the polyA tail is too short, mRNA is destroyed

3. splicing

   - exon joined together

what mature mRNA that codes for protein contains

Untranslated regions at 5’ and 3’ ends (5’ UTR, 3’ UTR)

• important for regulating translation

• sequences in UTRs are not translated

• protein bind here to control when/how much translation

translated region

• begins with a start codon and ends with the stop codon

codon

• groups of 3 nucleotides

• specify the order and identity of amino acids in a protein sequence

**in mRNA are read as NON-OVERLAPPING sequence

genetic code

____ _____ tells us which amino acid corresponds to each codon

• reads codons as written in mRNA

• AUG is ALWAYS the starting codon

• 1st amino acid is ALWAYS met

• 3 stop codons:

  • UAA

  • UAG

  • UGA

redundant

the genetic code is _____

universal

the genetic code is essentially ____

• the same code is used for most viruses, prokaryotes, and eukaryotes.

the 4 steps of translation

1. tRNA charging

2. initiation

3. elongation

4. termination

tRNA structure

• single stranded RNA

• stem-loop structure formed by base-pairing within tRNA

• anticodon loop

  • 3 bases that hydrogen-bond with codon bases in mRNA

  • complementary to codon

  • anti-parallel to codon

• amino acid binds to 3’ end

  • “tRNA charging“

  • 20 different enzymes in the cell do this (1 for each amino acid)

initiation

• ribosome binds mRNA and scans down from 5’ cap looking for start codon

• 1st tRNA anticodon binds mRNA codon AUG

strands are antiparallel

tRNA anticodon 3’-UAC-5’

mRNA codon 5’-AUG-3’

elongation

• amino acids are joined together to make polypeptides

• series of repeated cycles that each add one amino acid to new protein

  1. charged tRNA enters the ribosome on the right

     - proteins called elongation factors (EFs) help

     - anticodon of tRNA hydrogen-bonds with codon of mRNA

  2. peptide bond forms between amino acids

     - a covalent chemical bond that holds amino acids together

  3. translocation

     - ribosome moves down one codon in mRNA 5’ —> 3’

  4. steps 1-3 repeat until ribosome reaches stop codon

termination

• the 3 stop codons are not recognized by any tRNAs (UAA, UAG, UGA)

• proteins called release factors (RFs) bind

• ribosome leaves mRNA

gene expression

______ _______ can be regulated at many different steps

• allows different cell types to express only necessary genes

• allows cells to respond to their environment by making the right proteins at the right time