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Molecular Genetics And Genomics > Week 1 > Flashcards

Week 1 Flashcards

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0
Q

What is DNA?

A

The hereditary material in humans and other organisms.

Hereditary means information that is transmitted genetically from parent to offspring.

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1
Q

Where is genetic information stored?

A

In chromosomes in the cell nucleus

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2
Q

What does DNA consist of?

A

Nucleotides which contain a phosphate group, a sugar group and a nitrogen base.

Nucleotides are held together by weak hydrogen bonds

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3
Q

What are the purine bases?

A

Adenine and guanine

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4
Q

What is the family of nucleotide bases that contains thymine and cytosine?

A

Pyramiding bases

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5
Q

What are the pyrimidine bases?

A

Thymine and cytosine

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6
Q

What are the family of nucleotide bases that contain adenine and guanine

A

Purine bases

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7
Q

Where are the haploid human genome contained?

A

In the sperm and egg cells

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8
Q

The haploid human genome has..

A

A single set of chromosomes and 3 billion base pairs of DNA

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9
Q

Where are diploid human genome found?

A

In somatic cells

(Any biological cell forming the body of an organism, in a multicellular organism, any cell other than the gametes or an undifferentiated cell)

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10
Q

A diploid human genome contains…

A

Two sets of chromosomes (23 x2) and 6 billion base pairs of DNA

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11
Q

How much DNA do two unrelated individuals share?

A

On average 99.9%

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12
Q

Nucleotides pair together, what bases pair together?

A

Adenine - thymine

Cytosine - guanine

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13
Q

What is a gene?

A

Genes are the basic unit of heredity

Made up of DNA and act as instructions to make proteins which control cell function

Each person has at least two copies of each gene (one from mum and one from dad)

Recently 20000 (20,687)protein coding genes have been identified

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14
Q

With regards to the structure of a gene what can the nucleotide sequence do?

A

Nucleotide sequences define the structure of a gene and confer certain properties.

(Example TATA sequence in the promoter region binds several types of transcription factors which regulate gene expression).

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15
Q

Where are promoter regions located?

A

In the 5’flanking region

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16
Q

What happens in promoter regions?

A

RNA polymerase and transcription factors bond to the promoter to initiate production of an mRNA transcript

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17
Q

Who was the first scientist to make a key discovery about genetics & what was it?

A

Gregor Mendel (1856-1865)

Individual traits are determined by the inheritance of discrete “factors” (later called genes)

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18
Q

How has genetic knowledge been used for 1000s of years?

A

Farmers have known about the inheritance of traits from parents by using selective breeding to enhance crops and livestock.

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19
Q

What is ‘blending’

A

During the 19th century, hypothetical idea of inheritance by blending was popular. This was the idea that inherited traits blend from generation to generation

20
Q

How did Mendel show that blending was unlikely?

A

In his pea plant experiments certain traits were found to show up in offspring without any blending of parent characteristics

E.g. Yellow and green pea plants did not produce yellow-green peas

21
Q

What is Mendels law of segregation?

A

Each individual has a pair of alleles for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to its offspring

22
Q

What is Mendelian law of dominance?

A

An organism with alternate forms of a gene will express the form that is dominant.

23
Q

What is Mendelian law of independent assortment?

A

Separate genes for separate traits are passed independently of one another from parents to offspring

24
Q

What did Johann Miescher discover in 1869?

A

Identified weakly acidic substance in human nuclei he calls nucleons (later called DNA)

25
Q

How did Johann Miescher discover nucleic acid?

A

Studied the chemistry of the nucleus using leukocytes

Used different salt solutions to extract and purify the nucleus

Applied an alkaline extraction followed by an acidification to produce a precipitate which he called ‘nuclein’

Nuclein contained phosphorous and nitrogen

(Unknown function)

26
Q

What did Walter Fleming discover in 1882?

A

Discovered chromosomes

(Used coloured dyes to identify thread-like structures in the cell chromosomes (“coloured bodies”)

Investigated cell division and the distribution of the chromosomes to the daughter cells

27
Q

Who discovered hat chromosomes are the carriers of genetic material?

A

Boverti-Sutton chromosome theory (1902) identified chromosomes as the paired factors of inheritance predicted under Mendelian laws of inheritance.

28
Q

What did Frederick Griffith show?

A

Showed that genetic information can be transferred from heat killed bacteria to live bacteria. Process called “transformation”

29
Q

What is the DNA process transformation?

A

It is the process where Bacteria can take up foreign DNA from the environment.

30
Q

Explain Frederick Griffith’s (1928) study exploring transformation

A

Two strains of bacteria (S and R)

S was virulence (had the ability to cause disease) and had a smooth capsule putter coat

R was nonvirulent and had a rough appearance and no capsule.

When testing on mice he discovered that heating S strain the bacteria became inactive and didn’t kill the mice.

However when injecting the heated S strain with the R strain the nice died. (Neither of which caused the mice to die if injected alone)

He sampled the bacteria from the dead mice and he observed that it had the smooth capsule characteristics of the S strain.

He concluded that the S strain somehow transformed the R cells into the virulent S form. This process is known as transformation.

31
Q

Who extended Griffiths work on transformation?

A

Avery, Macleod and McCarty (1944)

32
Q

What did Avery et Al., (1944) explain?

A

Identification of DNS as genetic material used during transformation.

They had the heat killed virulent strain of bacteria

Added to that an enzyme that would destroy either:
RNA
Proteins
DNA
Lipids
Carbohydrates

Add this to the R strain bacteria

And only the sample with the DNase added did not transform the S strain bacteria (I.e. The mouse didn’t die)

33
Q

Who confirmed that DNA is the genetic material? And what was hypothesised previously?

A

Hershey and Chase (1952)

Previously thought that it was likely to be proteins

34
Q

What is a bacteriophage?

A

It is a virus that infects and replicates within a bacterium.

So it’s a virus for bacteria and it is made up of a small amount of DNA and proteins. It looks a bit lie a robot bug with a diamond head. It basically gets its DNA into the host cell and forces the host to reproduce the bacteriophage and eventually dissolves the walls of its host to get out and find new victims.

Note back this is one example of a phage others work in slightly different ways.

35
Q

Explain the Hershey-Chase experiments (1952)?

A

They labelled one lot of phages DNA with radioactive label and another lot the protein coats got radioactively labelled

They then got the phages to infect bacteria with genetic material

And they saw that the radioactivity enters he cell on the DNA labelled trials.

Thus tentatively suggesting that the genetic material is contained in the DNA not the proteins.

36
Q

Who discovered the double helix structure of DNA?

A

Francis crick, James Watson, Maurice Wilkins and rosalind Franklin. (1953)

37
Q

Explain the four main features of DNA as discovered by Crick, Watson, Wilkkns and Franklin (1953)

A
  1. DNA is a double-stranded helix, with two strands connected by hydrogen bonds (C=G, A= T)
  2. Most DNA double he lives are right handed (thumb -axis of the helix and fingers - sugar-phosphate backbone)
  3. DNA double helix is anti parallel - 5’ end of one stand is paired with the 3’ end of its complementary strand
  4. Outer edges of nitrogen-containing bases are exposed - available for potential hydrogen bonding, providing easy access to the DNA for other molecules.
38
Q

Who and when accurately counter the number of chromosomes humans have?

A

Tjio (1952)

46 not 48 as previously had been thought

39
Q

What is the central dogma of molecular genetics?

A

DNA -> RNA -> Protein

DNA is converted to RNA (transcription) and then to protein (translation)

40
Q

What is mitosis?

A

Mitosis is the process of separating the chromosome in its cell nucleus into 2 identical sets, in 2 separate nuclei

41
Q

Explain transcription and translation

A

Transcription begins with a bundle of factors assembling at the start of a gene to read off the information that is needed to make a protein.

A molecule unzips the double helix and copies one of the two strands letter by letter (the copy chain or the complementary strand is RNA)

The RNA needs to then be edited before it can be translated into a protein

This editing process is called splicing which involves removing the noncoding regions called introns from the gene leaving only the protein coding exons.

Splicing begins with an assembly of factors at the intron exon borders which act as beacons to guide small proteins to form a splicing machine called the spliceosome.

Introns are cut out released and exons are joined together this process is repeated for every intron in the chain and then when the RNA sequence just contains exons which are the complete gene sequence the chain is released

The RNA then snakes out of the nucleus to the outer part of the cell. Then all of the components of a molecular factory called a ribosome lock together around the RNA. It translates the genetic information in the RNA into a string of amino acids that will be come a protein (transfer molecules bring the amino acids to the ribosome).

42
Q

What is DNA replication?

A

Replication occurs at a localised region called the relocation fork, which is a Y shaped structure where new DNA strands are synthesised by a multi-enzyme complex.

The first step is the separation of the two strands by an enzyme called helicase. Helicase spins the incoming DNA to unravel it.

The two strand are labelled 3’ and 5’ depending on the direction in which their component nucleotide join up.

3’ is the leading strand, and is the easier to replicate. 5’ is called the lagging strand and requires a more complicated process as its effectively being copied backwards

Free nucleotides base pair to original polynucleotide.

DNA polymerase enzymes joins the sugar phosphate backbone

Repair mechanisms repair any incorrect additions to the polynecleotide chain

An enzyme rewinds the double helix

Two new double helices each contain one of the original polynucleotides.

43
Q

What is meiosis?

A

Meiosis is a special kind of cell division necessary for sexual reproduction in eukaryotes (all living organisms other than the eubacteria and archaebacteria).

Reduces the Moran diploid cells to haploid cells, enable sexual recombination to occur.

44
Q

What is RNA?

A

Similar to DNS molecules but it’s single stranded, made of ribonucelotides instead of nucleotides. Has the same bases as DNA except thymine is replaced with uracil.

Messages RNA (mRNA): congrats genetic information from DNA to the ribosome outside the cell nucleus.

45
Q

What is a protein?

A

Large biological molecules consisting of one or more chains of amino acids. Most polypeptides are combined with others and folded to produce complex protein as

Perform a vast array of functions within living organisms, including catalysing metabolic reactions, responding to stimuli and transporting molecules from one location to another.

46
Q

When was the birth of molecular genetics?

A

1970

47
Q

What are the three branches of genetics?

A

Classical genetics (before 1970 mainly based on onserving phenotypic inheritance), molecular genetics (furthered our knowledge on understanding of genes and their behaviour) and population/evolutionary genetics (quantitative genetics) (tries to answer questions about gene behaviour at a population and evolutionary level.

48
Q

What is genetics and genomics?

A

Genetics investigates the function and composition of single genes

Genomics addresses all genes and their interrelationships to identify their combined influence on the organism.

Molecular Genetics And Genomics (5 decks)

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