DNA and Gene Regulation

The shape of DNA was unknown until the early...

1950s

James Watson and Francis Crick using information from who's studies on DNA structure determined the structure of DNA

Rosaline Franklin

Watson has been stripped of academic titles after repeating what

offensive racist views

What does DNA stand for

Deoxyribose Nucleic Acic

What does DNA hold

the instructions for all living things

A DNA molecule is a double helix with two strands made up of a long string of what

nucleotides

Nucleotides have three pieces. What are they

5 carbon sugar

phosphate group

nitrogenous base

What are the DNA base pairing rules

adenine can only bond with thymine

guanine can only bond with cytosine

Each strand of DNA in a double helix is

complementary

DAN is an __________ double helix

antiparallel

What two sides do nucleotides have

a 3' and a 5' side

Each half of the DNA molecule (strand) run in the opposite direction from the other. what is this called

antiparallel orientation

Each strand is attracted through hydrogen bonds to the other strand. what are these attractions

A with T

C with G

DNA is wrapped around proteins called ___________ like beads on a string

histones

Once DNA is wrapped around a histone, the complex is called what

a nucleosome

Nucleosomes are then coiled together to create what

chromatin

Chromatin is further __________ and _____________

coiled

compacted

To replicate, the DNA molecule must

unzip

Each strand serves as a what to build a new strand following the base-pairing rules

template

Genetic instructions are passed down via what

DNA replication

New DNA molecules are made up of one strand of the __________ _________ and one strand that was ________ ____________

original molecule

newly synthesized

As a result of DNA molecules being made up of one strand of the og molecule and one strand that was newly synthesized, DNA replication is called

semi-conservative

In a DNA double helix, what can bond with what

adenine can only bond with thymine

guanine can only bond with cytosine

What are the three steps of DNA replication in eukaryotes

1. DNA is unzipped by helicase (hydrogen bonds break the strand and a replication fork is created)

2. New DNA bases are added by DNA polymerase (this enzyme reads a template strand and matches the complementary nucleotides. One strand is "lagging" and one strand is "leading"

3. DNA pieces are stitched together by ligase

DNA polymerase is not perfect. It will sometimes match up the _________, however proof-reading does occur, which means

wrong bases

most errors are immediately fixed

If an error is not caught, what two things might happen

mismatch repair

nucleotide excision

What happens if mismatch repair or nucleotide excision doesn't work

mutations

DNA houses the information necessary for what

how to build proteins

Proteins are what build most of the

functional units of cells and allow chemical reactions to happen

A gene is a segment of DNA which codes for a

specific protein

RNA is also a nucleic acid (like DNA). what does it stand for

Ribonucleic Acid

RNA has three major differences. what are these differences

1. single stranded (not a helix)

2. Sugar in RNA is ribose

3. Thymine is replaced by uracil

Why is DNA able to act as the molecule of heredity

because it can direct the production of proteins

DNA first directs the production of ___, which in turn controls what

RNA

the manufacture of proteins

After DNA first directs the production of RNA, proteins then perform the majority of

cellular functions and control physical traits

Genetic information flows from DNA to RNA to protein in two steps. what are these two steps

transcription and translation

Transcription follows the DNA base-pairing rules with one exception. what is this exception

uracil is used instead of thymine

the molecule that results from transcription is called

messenger RNA (mRNA)

What is transcription

the process of making an mRNA copy of DNA

What are the three steps of transcription

1. Initiation

2. Elongation

3. Termination

What happens during initiation (transcription)

RNA polymerase separates DNA strands creating a transcription bubble. It reads the DNA template strand to make new mRNA strand starting at a region called the promoter.

What is the promoter

a sequence of DNA, usually TATATA that RNA polymerase recognizes as its start location

What happens during elongation (transcription)

RNA polymerase continues synthesizing a copy of DNA using the template strand. mRNA is constructed in the 5' to 3' direction

What happens during termination (transcription)

RNA polymerase dissociates from the template DNA strand at the termination sequence (the sequence of DNA "recognized" as the end of the gene). In eukaryotes, the mRNA transcript is processed before leaving the nucleus

What happens during RNA processing

Introns (non coding pieces) are removed

Exons (coding pieces) spliced together

5' G cap

3' poly-A tail

The mRNA molecule serves as instructions for what

making a protein

At the ribosomes in the cytoplasm, each mRNA codon is

translated into an amino acid to build a protein

Translation involves the coordination of three kinds of RNA, which are

mRNA (messenger RNA)

rRNA (ribosomal RNA)

tRNA (transfer RNA)

Translation is done in the _________ by _____________

cytoplasm

ribosomes

Ribosomes are made up from what two things

rRNA and protein

Ribosomes read

mRNA

mRNA contains the code to make

proteins in the form of codons

What is a codon

a three letter nucleotide sequence on mRNA that codes for one amino acid

Each mRNA codon matches one of

20 amino acids

One end of the tRNA does what

carries amino acids to the ribosome

The other end of tRNA has an anticodon which is

complementary to the codon found on mRNA

The genetic code uses

triplets

DNA letters are read in a ________ code and every three nucleotides codes for

triplet

one amino acid

How do you read the genetic code

locate the 1st letter in the "first letter column"

then find the 2nd letter in the top row column

and so on

When does translation begin

when two subunits of a ribosome assemble on an mRNA

After two subunits of a ribosome assemble on an mRNA, what happens

a transfer RNA (tRNA) then brings in amino acids that match the codon in the mRNA

The first amino acid is always which amino acid ? what is the start codon

methionine (met)

UAC

The second tRNA assembles and the ribosome does what

catalyzes bond between methionine and the second amino acid

During translation, the ribosome does what

it moves over 3 bases on mRNA exposing a new codon, and the first tRNA is released

Elongation continues until the ribosome reaches a ___________________________. What are the stop codons

stop codon on the mRNA

UAA, UAG, UGA

What happens after elongation stops

the ribosome machinery then disassembles

The completed polypeptide (after elongation) is now available to be

used or modified by the cell into a functioning protein

What is gene regulation

the process of turning genes on and off

Different cell types express different genes, for example

not all cells need lactase (enzyme that digests milk)

Gene regulation in transcription... transcription factors bind to DNA to

"turn on" transcription

Gene regulation in translation... cells can control what

whether translation proceeds

how proteins are modified after translation

when proteins are broken down

A signal from another call can

regulate genes (turn on or off) in the receiving cell

What is a mutation

any change in the nucleotide sequence of DNA

Replacing, deleting, or adding a nucleotide base can

have a wide range of effects

Mutations are the

raw material of evolution by natural selection

most mutations are

harmful

Mutations can be

Spontaneous

induced by mutagens (high energy radiation, chemicals)

Point mutations occur at a

single nucleotide

Point mutations can have

varying effects

What is a silent mutation

alters a base but does not change the amino acid

What is a missense

A single change in the DNA sequence which results in one difference codon, and possibly a different amino acid in the polypeptide sequence.

- The protein's function might change, depending on whether or not the change results in a different amino acid.

What is a nonsense

improperly placed stop codon (premature stop)

Frameshift mutations are due to what

the addition or deletion of a nucleotide

Frameshift mutations often result in what

different or defective proteins