Micro Bio Final Module 8

Define genetics

The study of genes

Define Genes

Segments of DNA coding for a functional product

Define Chromosomes

A structure made of DNA that contains the genes

Carries hereditary info.

Define Genome

All genetic info. in a cell

Define genomics

The molecular study of genomes

Define genotype

The genes of an organism

Define phenotype

The expression of genes

The DNA molecule is composed of building blocks called ________

The polymer of DNA is _______ _____

Nucleotides

Nucleic Acids

What 3 things does every nucleotide consist of?

1) 1x sugar

2) 1x phosphate group

3) 1 of 4 bases (adenine, guanine, cytosine, thymine)

What does it mean to say that the two strands in a DNA double helix are anti parallel?

The sugar phosphate backbones run in the opposite direction

What type of bond holds complementary bases together of adjacent strands of DNA?

Hydrogen Bonds

What type of bond holds the backbone on a DNA strand together?

Covalent bond

What is a template? (in regard to DNA)

Strand of DNA “read” by enzymes to make new complimentary strands

True or False? Multiple replication forks are possible on a chromosome?

True: Multiple replication forks unwind simultaneously & new strands are going to be made simultaneously in both directions

What is the role of helicase?

Unwinds DNA

What is the role of DNA polymerase?

Adds nucleotides to a growing chain

(also “edits” out mistakes)

What is the role of DNA ligase?

Joins small fragments into a continuous chain

DNA polymerase only adds nucleotides to which end of the growing nucleotide chain?

Only goes 5’ to 3’

(5 prime to 3 prime)

What is transcription?

DNA → RNA

What is the function of DNA gyrase?

It separates the 2 circular DNA strands

Is DNA gyrase used in Eukaryotic cells, Prokaryotic cells, or both?

Only used in prokaryotic cells

Bacteria replicate DNA using _____ (which greek symbol) replication

Theta

How many nucleotides are used in a codon?

3 nucleotides per codon

What does it mean to say that the genetic code has redundancy?

Multiple codons can mean the same amino acid

What does it mean to say that the genetic code is unambiguous?

Any codon for 1 amino acid does NOT code for another amino acid

What is the name of the site on DNA where RNA polymerase binds to initiate transcription?

Promoter

What is the 1st stage of transcription?

Initiation: occurs at the promoter, a specific DNA sequence upstream of the gene

What is the 2nd stage of transcription?

Elongation: Appropriate RNA is inserted at the promoter

What is the 3rd stage of transcription?

Termination: Transcription finishes when RNA polymerase reaches the end & falls off DNA

How is transcription terminated?

When the RNA polymerase reaches a sequence called the terminator & falls off the DNA

Which segment of an mRNA transcript is removed before it is translated?

Terminator

What is the name of the process that removes segments of RNA?

Termination

Translation converts the information stored in _______ _____ to _____ _____

Nucleic acids → Amino acids

What molecules has the anticodon?

tRNA has anticodon

What organelle is the site of translation?

Ribosome

What is the 1st stage of translation?

Initiation: mRNA binds to small ribosomal subunit

What is the 2nd stage of translation?

Elongation: Addition of amino acids to the growing polypeptide chain

What is the 3rd stage of translation?

Termination: elongation halts at a “stop” codon

What is a polyribosome?

Many ribosomes bound along the length of an mRNA

What do we call the genes that are essential and always expressed?

Constitutive genes

What do we call the genes that are only expressed as needed?

Adaptive genes

For adaptive genes, what kind of genes are influenced by substrate concentration, are used to conserve energy, and the default position is OFF?

Inducible genes

In bacteria, what name is given to a cluster of genes with related functions, along with their control sequences?

Operon

In bacteria, what is the name for the DNA segment that is the regulatory “switch”, positioned within the promoter?

Operator

What is the name of the 1st gene controlled by the lac operon?

lac Z encodes beta-galactosidase: hydrolyzes lactose

What is the name of the 2nd gene controlled by the lac operon?

lac Y encodes permease: lactose membrane transporter

What is the name of the 3rd gene controlled by the lac operon?

lac A encodes transacetylase: modifies toxic galactosides

What is the lac I gene used for?

It is a lac repressor

Is the lac I gene a constitutive or an induced gene?

Constitutive gene, always transcribed

Explain how the lac operon gets activated and begins transcription

Allolactose = lac operon inducer

Binds lac repressor

Inactivates its function

Thus allolactose indues the lac operon

What is the name for proteins that inhibit transcription?

Repressor protein

Under what conditions would the trp operon be OFF?

Low tryptophan levels

Under what conditions would the trp operon be ON?

High tryptophan levels

What are the three characteristics of feedback inhibition?

1) Affects enzymatic activity

2) Fast acting

3) Short-lived effect

What are the three characteristics of feedback repression?

1) Affects enzymatic production

2) Slower response time

3) More enduring effects

When a mistake is made in DNA replication and not corrected, what is this referred to as?

Mutation

What is a point mutation?

Mutation that changes the DNA sequence by one or a few nucleotides

What is a base-pair substitution mutation?

A mutation that does not change the # of nucleotides

What is an insertion mutation?

Mutation that produces a frameshift mutation

What is a silent mutation?

Mutation that does NOT change the amino acid

What is a missense mutation?

Mutation where 1 amino acid is changed

What is a mutagen?

Agent that causes mutations

What is a spontaneous mutation?

A mutation that occurs in the absence of a mutagen

Define vertical gene transfer

Occurs during reproduction between generations of cells

Define horizontal gene transfer

Transfer of genes between cells of same generation

What types of genes can be transferred in horizontal gene transfer that give bacteria some sort of advantage?

Temp. resistance

pigmentation

antibiotic resistance

What are the 3 types of horizontal gene transfer?

1) Transformation

2) Transduction

3) Conjugation

Define plasmids

Additional genetic material that carry non-essential genes