Molecular genetics Flashcards
Define a chromosome
a condensed DNA molecule that carries genetic information
In DNA , What is a double strand nucleotide formed from?
Phosphate, sugar and nitrogen bases (A&T and C&G)
What tupe of bond holds together the complimentary nitrogen bases
Hydrogen bonds
Whats a double helix
Two strands of DNA held together by hydrogen bonds that form a spiral shape
which molecules form the backbone and rungs of the double helix
Backbone: sugar & phosphate
Rungs: nitrogen bases
Whats a anti parallel mean in double helix
the two strands that make up the double helix run in opposite directions
What is Mitochondrial DNA ? (mtDNA)
DNA found in all cells passed down in the egg cell from the mother , genetically identical to your mother
What is RNA
> made of
> structure and tole
Ribonucleic Acid
> sugar phosphate and nitrogen bases (U with A , no Thymine , C and G
>Single stranded plays a role in protein synthesis
What does the endosymbiont theory suggest
That both mitochondrial and chloroplast DNA were engulfed by anaerobic cells w nucleus and evolve very slowly
Who is Miescher and what did he find/do
Isolated DNA from white blood cell nuclei in 1869
Who is Chargaff and what did he find/do
In 1940s looked at DNA from different species and found that A and T are always in same proportion; as are C and G
(A=T , C=G)
Who is DNA structure determined by and how
Franklin, Watson , Crick and Wilkins determined DNA structure of double helix by using x ray crystallography
What is DNA structure : parts
DNA is 2 stranded: double helix
A and T same : C and G same
Who is and What did Franklin find
British scientists in 1950s , used x tay photography to find DNA double helix structure with repeating patterns with nitrogen bases on inside and sugar phosphate on outside
Who are Watson and Crick , what did they do
Scientisys that sere awarded for publishing g Franklins work: credited for double helix DNA and structure
Structure of DNA:
> DNA consists of?
> What is on each side?
> What is backbone?
> Whats a double helix?
>What are rungs and strungs of DNA ladder?
> The DNA double helix twists in what direction?
> DNA consists of 2 strands of nucleotides
On each nucleotide contains a sugar, phosphate and nitrogen bases
sugar and phosphate are the backbone
2 strands of DNA that ars in twisted lafder structure
nitrogen bases ars rungs and sugar phosphate are struts of ladder
clockwise direction
What did Hershey and Chase ecperiment do and find out
Teated ti gind out wether the contents inside DNA or protein coating we’re getting passed onto daughter cells from infected parents
> found out DNA was the hereditary material which gets passed on from parents cells to daughter cell
How does DNA store information
in the form of nitrogen bases
What did Griffith find out
Heat killed pathogenic strain mixed with harmless strain acted to transform them into pathogenic strain
Why replicate DNA?
> when is it done, type
So cells can divide during mitosis and meiosis and that their daughter cells will be able to have correct amounts of DNA
> during S phase of interphase )> )(
is semi conservative (half original half new)
What is the structural unit that makes up DNA ?
Nucleotide
What does antiparallel mean
> 5 to 3
The teo strands that make up the double helix are run in opposite directions
Both run in 5 to 3 direction one is leading and one lagging
What is enzyme role
> direction
Involved in DNA replication
> Read or copy DNA in one direction: 5 to 3
DNA replication: Initiation phase
> what happens
> enzymes
Starts at replication origin
> Helicase enzyme binds to the double helix and separates it into two strips
( opens up regions of DNA. replication bubbles)
DNA Replication: Elongation phase
> what happens
> enzymes involved
Each old parent serves as a tamplate to make new complementary strand
> RNA primase enzyme : marks starting point for nucleotide attachment
> DNA polymerase attaches floating nucleotides to parent DNA ( matching up A and T or C and G) in a 5’ to 3’ direction
> on leading strand it already goes 5 to 3 continously
> lagging strand goes opposite way so it grows in chunks ( Okazaki fragments) in 5 to 3 direction that are joined after by DNA ligass
DNA Replication: Termination
> what happens
> structure
DNA automatically rewinds
> each DNa molecule has 1 parent strand and 1 new strand ( Semi conservative DNA)
each strand is x2 ( half new half old )
DNA proofreading and correction
> done by who
> how does it happen
DNA polymerase is the proofreader: incorrect nucleotides out replaced w correct one
> happens immediately after one part of DNA is formed
What are mutations
> mutagens
> inheritance
Mutations ate errors in DNA, likr changes is DNA sequence or mechanisms
> Mutagens cause mutations : ex . radiation, smoking
> inherited only if they occur in sex cells
In which direction are nucleotides added during replication
5’ to 3’ direction
What does the DNA enzyme Helicase do
Opens and unwinds DNA
What does the DNA enzyme primase do
Synthesizes primer to begin elongation process and tell polymerase where to go
What does the DNA polymerase enzyme do
Builds by adding nucleotides within replication bubbles so opposite letters pair up 3’ to 5’
What does the DNA ligase enzyme do
Glues together Okazaki fragments of lagging strand
What are genes
Specific segments of DNA on chromosomes
What is gene expression
The way that information in a gene is converted into a specific characteristic through the production of a polypeptide (protein)
What do proteins form
> what are polypeptides
Proteins form all skin, hair, muscles, enzymes in a cell
> products of all genes are polypeptides
What are proteins
> how many
Proteins are sequences of amino acids
> 20 different aa
How are aa joined together
> why?
They are joined together by dehydration synthesis , removing water to form peptide bonds > to form polypeptide chain
What is a Codon
> form
> how many
Code for each amino acid
> formed of 3 nucleotides
? 61 codon combinations make all 20 amino acids
What is RNA role
> types are
To convert the instructions in a gene into a polypeptide chain
> 2 types: Messenger mRNA and Transfer RNA tRNA
What is the main differences of RNA from DNA
- Different sugar than in DNA
- Instead of Thymine (t paired w a) RNA has the base Uracil that bonds with Adenine
- RNA is single stranded and van leave the nucleus unlike DNA which cant and is double stranded
What is the order of DNA to protein and names of processes
DNA > RNA is transcription
RNA > Polypeptide protein is Translation
What is and where is info carried:
1- Transcription
2 - Translation
1- Transcription is the process of converting DNA into MRNA , carried from nucleus to cytoplasm
2- Translation is process of synthesizing a specific protein as coded by MRNA in cytoplasm
What is the central dogma
The whole process of genetic info passing via transcription from DNA genes to RNA copy of the gene and the RNA then directs the sequential assembly of a chain of aa to produce a protein
Transcription
> where does it take place
> what happens
> steps
> takes place in nucleus
DNA sequence of gene is copied into single stranded mRNA
Initiation, Elongation and Termination
What happens in RNA
1- Initiation
2- Elonhation
3- Termination
4 -Processing
1- RNA polymerase binds to DNA at promoter region and opens up double helix
2- Builds single stranded mRNA in 5’ to 3’ direction , no primer required and U instead of T
3- Synthesis stops at end of gene : termination n sequence
4- Before mRNA can leave nucleus it must mature: Introns are non coding stuff and get cit out , stay in the nucleus
Exons do code for protein and go out of nucleus they r linked by Splicesomes
Translation:
> where dose it take place on ehat
> what happens
> the processes
> takes place in cytoplasm on ribosomes
Synthesis of protein under direction of mRNA, gene> protein
Initiation , elongation and Termination
During translation how is the mRNA read
> codon
Read in grps of 3
> Each codon calls for a specific aa to be placed that forms the protein
What are starting and stopping codons
Start: tells where translation begins , AUG codes for methionine
Stop: tells where translation stops, UAA or UGA or UAG , dosent code for any aa
Translation steps : Initiation , Elongation and Termination
1: Initiation - Ribosome recognizes start codon and binds to site , it moves in 5’ to 3’ direction adding aa each time it reads a codon brough by tRNA
2- Peptide bonds form between two aa, tRNA are recycled , process continues
3- Ribosome reaches stop codon , releasing factor protein recognizes this and help release polypeptide chain
When can mutations occur
> 2 types and what are tgey called
1- Chromosomal : occurs during crossing over in meiosis
2- Gene: Error in DNA caused by mutagens
> inherited if in reproductive genes ( gametes )
What are point mutations:
>Types
Error occurs in a single base pair : substitution bc base pair is swapped
> Silent: dosent change aa sequence
Mis sense : leads to production of 1 different aa
Nonsense: leads to pre mature stop codon and binds
What are frameshift mutations
> types
When a nucleotide is deleted or inserted in sequence and causes the change of whole thing
> Deletion: remove or Insertion: put extra
Whats a codon
3 nitrogen bases and 1 aa
What is recombent DNA
> how is it done
When gene from one species is transferred into the DNA of another organism
> Cut out the desired DNA sequence , cut by restricting enzyme
> Cut host DNA
> Insert and glue together done by ligase
What are restriction enzymes
Enzymes that cut DNA and leave sticky ends or blunt ends to stick better
What is ligase do
glue DNA
How are organisms used to produce therapies
primarly by bacteria used to make insulin or growth hormone
What are transgenic plants
genetically modified organisms GMOs , plants that have genes inserted for a desired look or to fight against viruses
What are vectors
common ones are
methods of transportation > introducing foreign DN- into genome of a living cell
viruses common vector
Whats DNA sequencing ?
> used for
> steps
DNA fingerprinting
> criminal identification
> collect DNA, Polymerase chain reaction: ampify make more DNA , cut out DNA into fragments with restriction enzymes
Last put into electrophoresis gel
