DNA, Protein, Mutations

Nucleotides

the repeating subunit that makes up DNA

DNA Nucleotide 3 Parts

1. Deoxyribose sugar

2. phosphate

3. Nitrogenous base

4 DNA Nitrogenous bases

Adenine, Thymine, Guanine, Cytosine

Who determined the relationship between nucleotides?

Erwin Chargaff (1950)

Chargaff's Rule

always same amount of Adenine as Thymine (same for C and G)

Who caught an X-ray Diffraction showing a DNA Double Helix?

Rosalind Franklin (1952)

Who discovered the DNA Double Helix model?

Watson and Crick (1953)

What forms the backbone of DNA?

Sugar and Phosphate

Nitrogen bases bond in the middle with weak _________ ____

Hydrogen bonds

All other bonds (Including the sugar-phosphate backbone) is made of what type of bond?

Covalent bonds

Nitrogen bases bond only to their __________

Complementary base pair

Complementary base pairing rules (DNA)

A bonds to T

G bonds to C

A _____ bonds to T

double

C _____ bonds to G

triple

Antiparallel

the strands run in opposite or antiparallel directions

1sd strand runs in a __' to __' direction

5' to 3'

2nd strand runs in a __' to __' direction

3' to 5'

Phosphate end is ALWAYS the __' end

5'

Deoxyribose sugar is always the __' end

3'

RNA structure

Single strand of RNA nucleotides with exposed bases

What type of sugar makes up RNA Nucleotides?

Ribose

RNA Bases

A with U

C with G

DNA Replication

the copying of DNA

Why must DNA copy itself before cell division in mitosis?

To give each daughter cell an exact copy of the DNA

Why must DNA copy itself before cell division in meiosis?

so each daughter cell gets one of each chromosome

Chromosomes

tightly coiled strands of DNA

Gene

a piece of DNA that has instructions to code for ONE protein

One chromosome can contain _______ of genes

thousands

What phase of the cell cycle does DNA replication occur

S phase (of interphase)

Enzyme ______ unzips the DNA

helicase

Openings in the DNA are called

origins of replication

Several places along the DNA will be unzipped at once. True or False?

True

Enzyme ______ _____ adds complementary nucleotides to template strands (DNA Replication)

DNA polymerase

DNA polymerase only adds nucleotides to the __' end of the template strand. This forms new DNA strands in the __' to ___' direction ONLY

3'

5' to 3'

Semi-Conservative Replication

in each new DNA double helix, one strand is from the original molecule, and one strand is new

DNA Polymerase 2 roles

1. enzyme that matches up and join nucleotides to the template to produce new strands of DNA.

2. Also proofreads new DNA to make sure no errors

"Job" of DNA

code for proteins

Which organelle makes proteins

Ribosomes

DNA can leave the nucleus. True or False

FALSE

How does mRNA exit the nucleus?

through nuclear pores

RNA's sugar

ribose sugar

mRNA

messenger RNA

A copy of the DNA code for a gene, carries the gene code from the nucleus to the ribosome

tRNA

transfer RNA

brings specific amino acids to ribosome

rRNA

ribosomal RNA

makes up structure of ribosome (along with protein)

Where does transcription occur?

in Nucleus

Transcription overview (3 step)

1. The DNA molecule unzips only in portion of the specific gene that will be copied.

2. A mRNA molecule created by the enzyme RNA polymerase makes a copy of the DNA's base sequence using RNA nucleotides.

3. the mRNA copy of the gene can leave the nucleus.

RNA Polymerase only binds to ______

Promoters

What tells RNA Polymerase to stop transcriping?

Terminator

Transcription Factors

1. Control rate of transcription: which genes and how often transcribed

2. Turn genes on and off. Control gene expression.

3. Help coordinate cell cycle

Where does translation occur?

Outside nucleus

Translation overview (4 steps)

1. mRNA attaches to a ribosome outside nucleus.

2. Ribosome reads the code 3 bases at a time (codon)

3. Codon on the mRNA matches the anticodon on the tRNA

4. A protein chain is formed.

Start codon

AUG - methionine

How many amino acids are there?

20

How many codons are there?

64

Proteins are made of??

Amino acids

Mutation

a change in DNA

Germ line or hereditary mutation

inherited from a parent and present in all the individuals cells

Somatic mutations

a mutation in somatic cells that can not be passed onto offspring. Caused by environmental factors.

Gene mutations / point mutations

changes in one or a few nucleotides that occur at a single point in the DNA sequence

Germ mutations only affect a _____ gene

SINGLE

Chromosomal mutations

changes in the number or structure of chromosomes

Types of Point Mutations

substitutions, insertions, and deletions

Frameshift mutations

insertions and deletions

Substitution

One base is changed to a different base. Only affects a single amino acid and may have no effect at all

Types of Chromosomal Mutations

Deletion: loss of all or part of chromosome

Duplication: extra copy of all or part of chromosome

Inversion: reverse the direction of parts of a chromosome

Translocation: Part of one chromosome breaks off and attaches to another

Nondisjunction

Failure of chromosomes to separate during cell division

When can nondisjunction occur

Can occur during mitosis (not genetic), meiosis I, or meiosis II.

Nondisjunction effects

Causes errors in chromosome #

Trisomy 21 (Down Syndrome) and monosomy X (Turners Syndrome

also common cause of early miscarriage

What Causes Mutations?

Errors in DNA replication, Cell division.

Mutagens: chemicals (ex. Pesticides, tobacco smoke) Physical agents (ex. radiation from x-rays or UV rays)

Mutations will only have effect if there is a change in the _________

phenotype

Eukaryotic Gene expression can be regulated at ___ stages

many

Eukaryotic Gene expression depends on _____ and ____ factors

internal, external

Main control point of eukaryotic gene regulation

transcription

TATA Box

part of a promoter sequence that binds a protein (transcription factor) that helps position RNA polymerase by marking a point just before beginning of a gene.

What do certain transcription factors do?

- open up tightly packed chromatin

- Attract RNA polymerase

- Block access to certain genes

________- transcription factors must bind before RNA polymerase is able to attach to the promoter and start transcription.

multiple

Homeotic/Hox Genes

master control genes that regulate body development during embryonic development