Molecular Genetics & Mutations- Biology 30 Alberta

Why is DNA important?

It contains a code that a cell uses to put together all the material it needs to function properly.

Where is DNA found?

in the nucleus, mitochondria, and chloroplasts

How many chromosomes do humans have?

46 (23 pairs from each parent)

How does DNA replicate?

Using RNA primers

Chargaff's Rule

[A]=[T] and [G]=[C], they pair up across from one another forming two strands also called base pairing.

1949; discovered that DNA contains equal amount of A/T and C/G (pyrimidines = purines)

Rosalind Franklin

1953; bombarded DNA with x rays to determine DNA’s helical structure

Watson and Crick

1953; concluded double helix structure; became accepted as molecular structure of DNA

What is the structure of DNA

double helix (twisted ladder)

What forms the backbone of DNA?

sugar and phosphate

What are the rungs of the DNA ladder made of?

nitrogen bases

Nitrogenous bases from one spine of a ladder are connected with the other nitrogenous base by means of

hydrogen bonds

The backbone of the molecule is alternating what

Phosphate, deoxyribose, a sugar

What makes a nucleotide?

sugar, phosphate, nitrogenous base

What is DNA made of

nucleotides

Replication of DNA

produces two molecules, each of which is half new and half old DNA joined lengthwise to each other.

Why is DNA replication called semi-conservative?

due to complimentary based pairings on the template strand the new DNA has one old strand and one new strand

What are the 3 steps of DNA replication

initiation, elongation, termination

What is initiation

Separating the strands

Helicase function (DNA replication)

Breaks the hydrogen bonds between the bases

Initiation of DNA replication

DNA is unwound at origin of replication by helicases producing two replication forks on either side

what is Elongation

the addition of amino acids to the polypeptide chain

What is termination

When DNA polymerase enzymes cut out incorrectly paired nucleotides and add the correct nucleotides.

Ligase

Molecular "glue"

Leading strand

The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.

Lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

What are proteins made of?

long chains of amino acids, What are the 2 steps for protein synthesis, Transcription and Translation

Explain transcription

Transcribe the DNA into mRNA

Explain translation

Proteins are made with individual amino acids (tRNA translates mRNA) .....it "reads" the message

What does RNA stand for?

ribonucleic acid

What does DNA stand for?

deoxyribonucleic acid

How is RNA different from DNA

Leaves the nucleus, sugar backbone is ribose not deoxyribose, has uracil instead of thymine, single stranded, can be either tRNA, mRNA, or rRNA

tRNA

type of RNA that carries amino acids to the ribosome

mRNA

type of RNA that carries instructions from DNA in the nucleus to the ribosome

rRNA

type of RNA that makes up part of the ribosome

Why do we need to make proteins

Move muscles, store nutrients, provide structural components

What is the role of DNA in protein synthesis

It is the blueprint for the amino acid sequences that make up different proteins expressed by the cells of the body.

What is a codon and where is it found?

Found on an mRNA, and three bases on the mRNA which code for an amino acid

Start codon

AUG (methionine)

Stop codons

UAA, UAG, UGA

Helicase

An enzyme that untwists the double helix of DNA at the replication forks.

What are the 3 steps in Transcription and Translation

Initiation, Elongation, and Termination

Anti-codon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

How does tRNA work?

tRNA has an anticodon and is charged with a specific amino acid. it finds the specific codon so that the anticodon can pair with it and then drops off the amino acid

Genes

Code for specific polypeptides (proteins) made by many amino acids

Genome

the complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes

Define mutation

Mutations are a permanent (can be inherited) change in the genetic material

Mitochondrial DNA is identical to what? What can it show?

Your mothers egg. It can be tracked to see if mtDNA matches, then your ancestry can be determined.

Mutations cause ___________

messed up DNa - mRNA - tRNA - amino acids - proteins -cells

Somatic mutations

Mutations that occur in body cells, aren't passed to offspring, and don't affect the gametes

Beneficial mutations

Enhance the survival or reproductive success of an organism. Tends to become more common over time, leading to an evolutionary change.

Harmful mutations

Produce characteristics that are harmful to the organism, occurs at low rates.

Neutral mutations

Produce neither adverse or helpful changes. Not acted on by natural selection.

Phylogeny

Evolutionary history of a species or group of species.

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Physical mutations

UV radiation, X-rays, gamma rays, asbestos etc

Chemical mutations

pesticides, carcinogens; nitrites, gas fumes, smoke.

How is cancer formed?

Uncontrolled cell division of unusable cells

Oncogenes

cancer causing genes that control cell growth and multiplication

Structural genes

genes that directly the assembly of amino acids into proteins

Regulatory genes

genes that act like a switch that turns “off” segments of a DNA molecule so the gene is only active when/where its gene product is needed

Gene Splicing/ Engineering

When genetic information from one organism is spliced into the chromosome of another; When to organisms that would or could never exchange genetic information are joined.

Restriction enzymes

Enzyme that cuts DNA at a specific sequence of nucleotides

Why are restriction enzymes important?

They are specific. They play a major role in the construction of recombinant DNA.

What is electrophoresis and when is it used

Technique used to separate DNA fragments. IT can be used for paternity suits, Identification, and or crime.

endonuclease

cuts DNA internally

Is it possible to create an organism with more than one species type of DNA?

Yes! It's called transgenic DNA; seen in medicinal bacteria, transgenic plants, and cloned animals

What is biotechnology?

It uses living things to make products for sale.

What is genetic screening?

the process of testing DNA to determine a person's risk of having or passing on a genetic disorder

amniocentesis

needle puncture of the amniotic sac to withdraw amniotic fluid for analysis

Gene therapy

The insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder

Gene cloning

The nucleus of an unfertilized egg is destroyed with radiation. a diploid nucleus from a body cell is placed into a irradiated cell then divides as if it were fertilized