Chapter Seven: Molecular Genetics Flashcards by Moksha Saripilli

What is bacterial transformation?

The ability of bacteria to alter their genetic make up by absorbing foreign DNA molecules from other bacteria and incorporating it into their own

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Which is the molecule of heredity?

DNA

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How did Hershey and Chase prove that DNA was indeed the molecule of heredity not proteins?

They tagged bacteriophages (bacteria attacking virus) with different isotopes, one for DNA other for protein coat. When bacteria were infected with the phages, the DNA isotope entered and produced progeny, but the protein isotope did not influence any radioactivity.

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Who continued the work of studying DNA structure from Maurice Wilkins, and who got this the Nobel prize?

Rosalind Franklin used X-ray crystallography analysis on DNA to show it to be a helix. Watson and crick used her work to develop their model

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What is semi-conservative replication?

A double-stranded molecule of nucleic acid separates into two single strands each of which serves as a template for the formation of a complementary strand that together with the template forms a complete molecule. So each replica consists of 1 new and 1 old strand

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What is dna’s twisted ladder like structure said to be?

Double helix

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What consists of the 2 opposite running complementary strands of DNA?

They each are polymers of nucleotides.

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What does each nucleotide consist of?

A 5-carbon sugar (deoxyribose)
A phosphate group
A nitrogenous base

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State the pairing of the bases

A-T

C-G

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What is the bond between bases?

Hydrogen bonds

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What are the 4 bases?

Adenine
Cytosine
Guanine
Thymine

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Which enzyme catalyses the replication of new DNA?

DNA polymerase

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When does replication occur in a cells lifetime?

Interphase (S-phase)

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What is another function of polymerase apart from catalysing?

Proofreading new DNA
Fixing errors
Minimising mutations

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Which enzyme unzips the hydrogen bonds connecting the strands?

DNA helicase

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On what basis does the new strand form on the old template?

Base pairing rules

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Some nucleotides are lost from ends of chromosomes. What do some eukaryotic cells do to protect these genes?

They have nonsense nucleotide sequences at the ends, repeated thousands of times.

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What are the protective ends of chromosomes called?

Telomeres

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State 3 ways in which RNA is different from DNA

It is a single stranded helix
Instead of Thymine, it’s got Uracil
ribose sugar not deoxyribose

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How is RNA similar to DNA?

it is a polymer of nucleotides

* the nucleotides have 5-carbon sugar $except it’s ribose), phosphate group, and a base

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What is messenger RNA?

mRNA carries messages directly from DNA to cytoplasm during protein synthesis

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What are triplet nucleotides (such as AAC,UUU) of RNA called?

Codons

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What is transfer RNA?

tRNA carries amino acids to mRNA at the ribosome to form proteins

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What are triplet nucleotides of tRNA, complementary to those of mRNA, called?

Anticodons

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What is rRNA?

Ribosomal RNA is structural and along with proteins makes up the Ribosomes

What is transcription?

Process by which DNA makes RNA, facilitated by RNA polymerase, which unzips the strand at the specific gene. Triplet code in DNA is transcribed into a RNA codon following base pairing rules; A with U, C with G

How is RNA processed before leaving the nucleus?

Enzymes remove pieces of RNA that do not code for any protein

What are removed regions of RNA called? Describe.

Interons - intervening sequences

What are remaining regions of RNA called? Describe

Exons - expressed sequences

What is translation?

mRNA sequence is converted into an amino acid sequence

How is translation done?

tRNA carry amino acids in the cytoplasm to codons of the mRNA according to base pairing rules

Why can some tRNA bind to 2 or more codons

Because many codons can code for one amino acid

Which amino acid does AUG code for?

Methionine

Which amino acid does UUU code for?

Phenylalanine

Which amino acid does GUU code for?

Valine

Which amino acid does CUU code for?

Leucine

Which amino acid does AGU code for?

Serine

Which amino acid does GGU code for?

Glycine

What is gene regulation?

The turning on and off of genes as per the cells requirement Eg insulin production

What is an operon?

A cluster of functional genes plus the switches that turn them on/off in a bacterium

What is the inducible operon?

An operon that's normally turned off unless actively triggered/induced by something in the environment

What is a repressible operon?

Is always turned on unless actively turned off because it is temporarily not needed

What is the promoter? And state it in terms of operon

The binding site of RNA polymerase. It is like an on switch

What is the operater? And state it in terms of operon

Binding site for the repressor. Turns off the inducible operon

What is the TATA (Thymine Adenine alternating sequence) box?

Helps RNA polymerase bind to the promoter

What are mutations?

Changes in genetic material

When do mutations occur?

They are random

What causes mutations?

Mutagenic agents ie toxic chemicals and radiation

What is a point mutation?

It is a base-pair substitution, where one nucleotide converts to another

Is sickle cell anaemia inherited or caught and developed?

It's genetic

How does sickle cell anaemia result (in terms of genes)

A point mutation in the gene that codes for haemoglobin

What is the effect of sickle cell anaemia and why?

Tissues are deprived of oxygen | Because the abnormal haemoglobin cause red blood cells to sickle when available oxygen is low

When a point mutation could serve as beneficial for an organism what is it called?

Natural selection

Do mutations in DNA always change amino acid sequence?

What is single nucleotide deletion?

Loss of a base

What is single nucleotide insertion?

Addition of a base

What do insertions and deletions result in?

Frameshift

What is frameshift and why can it be disastrous?

When the entire reading frame is altered and unreadable, causing altered or no polypeptide formation

What are chromosome mutations?

Alterations in chromosome number or structure

What is it called when there are abnormal number of chromosomes?

Aneuploidy

Official term for downs syndrome?

Trisomy-21

What is the mutation in Trisomy-21?

Extra #21 chromosome

What is polyploidy and how is helpful in flowers?

Having entire sets os chromosomes (3n, 4n) | Large bright coloured flowers

What do aneuploidy and polyploidy result from?

Nondisjunction

What is genome?

Organisms genetic material

How many genes do humans have?

20,000

What are pseudogenes?

Former genes that have accumulated mutations over a long time

In the 97% of DNA not used for protein coding, state 3 thing other than pseudogenes

- regulatory sequence (control gene expression) - introns (interrupt genes) - repetive sequences that may never get transcribed (Telomeres)

What is recombinant DNA?

Taking DNA from 2 sources and combining them in one cell

What is genetic engineering?

Branch of science using recombinant DNA

2 concerns behind genetically modified organisms?

- they may spread the engineered genes to wild species | - they may adversely affect people who eat them

How can gene therapy be used to treat genetic diseases?

Insert functioning genes into cells to replace non-functioning ones eg CF and SCA

How is environmental cleanup done with genes?

Mircobes are being engineered to degrade oil at oil spills or decontaminate harmful chemicals toxic mines

What are restriction enzymes?

They cut DNA at specific recognition sequences of sites

What are pieces of DNA resulting from restriction enzymes called?

Restriction fragments

What is gel electrophoresis?

It separates large molecules of dna on the basis of their rate of movement through an agarose gel in an electric field

Relate molecule size and rate of movement through the gel

The smaller it is, the faster it runs

What can be changed to provide a better separation of tiny DNA fragments ?

Concentration of the gel

How is DNA prepare before it's put in gel?

It's cut up by restriction enzymes, pieces small enough to migrate though the gel

What is polymerase chain reaction?

It is an automated technique where by many copies of a specific dna can be copied or amplified in vitro using heat-stable enzymes and then be studied/compared with other dna samples

What is Frameshift?

mutation in which a number of nucleotides not divisible by three is inserted or deleted so as to changethe reading frame of some tripletcodons

What proportion of genes are in the mitochondria?

8/15 | 16000/30000

Where are restriction enzymes extracted from?

Bacteria | NOT there in humans