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DNA, Genes and Chromosomes

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Adam Jolly

on 1 November 2016

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Transcript of DNA, Genes and Chromosomes

Covering points 3.13 to 3.32
Chromosomes, Genes and DNA
Chromosomes, Genes and DNA
Chromosomes
Genes
Inheritance
How we're put together.
DNA
Coding and Replication
Mutations
What do you think a mutation could be?
A mutation is a change in the DNA code within a cell
If the code changes, then the wrong codon is used. This can alter the sequence of amino acids, when they are combining to form a protein.

There are 4 types of DNA mutations.
Duplication:
Deletion:
Substitution:
Inversions:
the nucleotide is inserted twice instead of once, during replication
a nucleotide is missed out during replication
a different nucleotide is used
the sequence of bases in a triplet is reversed
What could each of these mutations cause?
Deletion
Duplication
Inversion
Substitution
Only one side of the DNA molecule codes for the manufacture of proteins in a cell. this is called the sense strand, the other is called the anti-sense strand

(I like to call it the nonsense strand)
Coding
Three nucleotide bases form a
CODON
, which codes for one specific amino acid.

For each protein, its specific amino acid structure is reflected by its codon sequence.

Codons are universal. The same codons code for the same amino acids in any living organism.
Replication
During mitosis, a cell must first make an exact copy of each DNA molecule in the nucleus. This is called
REPLICATION
Mutations
Entire base sequence altered. 'Frame-shift'. Whole gene different, different protein made.
Base sequence altered. Again frame-shift occurs. Whole gene and protein different.
Different triplet codon may code for another amino acid or it may not. Structure of protein could be different. Could produce a different form, function or lack of function for a protein
Similar effects to substitution. Generally only one triplet affected.
Mutations
The majority of mutations (99.9%) cause cell death as they change protein function to the extent that the cell cannot survive. However some mutations can confer an advantage to that organism, e.g. antibiotic resistant bacteria...
Each chromosome is one long strand of DNA.
It is coiled tightly around protein molecules called
HISTONES
Nearly all human cells contain 46 chromosomes that we group into 23 pairs.
Chromosomes
Cells that contain 46 chromosomes are called DIPLOID
Gametes have exactly half the number of chromosomes, and are called HAPLOID. They are formed by meiosis.
and alleles
A gene is a section of DNA that makes a particular protein.
Each protein contributes to a particular feature, be it visible or not.
Alleles
An allele is a different form of the same gene.

They are located in the same place in homologous chromosome pairs.

The homologous pairs carry all their genes in the same sequence, but the alleles might not be the same.
CHROMOSOME MUTATIONS
KEY WORDS
Gene

Allele

Dominant

Recessive

Homozygous

Heterozygous

Phenotype

Genotype

Codominance
The characteristics of the organism. Determined by the genotype.
The alleles that each cell has for the particular gene in question.
The alleles that the cell possesses are exactly the same for the given gene
The alleles that the cell possesses are different for the given gene
The allele that is expressed when in a cell
The allele that is normally suppressed, but when homozygous,
is expressed.
Two alleles that can contribute to the phenotype when combined.
PREP
What is antibiotic resistance?

How do bacteria become resistant to antibiotics?

Who discovered Penicillin and how does it work?

What does MRSA stand for and what does it mean?

Why is antibiotic resistance a problem for humans?

MITOSIS
Mitosis is the process by which a cell duplicates its DNA, to form 2 identical sets of chromosomes.
The cell can then split into two new cells with two new genetically identical nuclei.
Genetic Modification
KEY WORDS
RECOMBINANT
DNA from two different organisms that has been stuck together.
TRANSGENIC
An organism that receives recombinant DNA that contains DNA from another organism.
RESTRICTION
ENDONUCLEASE
Enzymes that cut DNA at specific points. They are used to 'cut out' specific genes.
DNA LIGASE
Enzymes that stick together cut ends of DNA molecules.
Plant modification
The Birth of Genetics
Gregor Johann Mendel
(20 July 1822 – 6 January 1884)
Between 1856 and 1863, he conducted experiments breeding pea plants.

Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color.
Mendel coined the terms “recessive” and “dominant” in reference to certain traits. He published his work in 1866, demonstrating the actions of invisible “factors”(now called genes) to cause visible traits in predictable ways.
A gene is a section of DNA that makes a particular protein.
An allele is a different form of the same gene.
Understanding inheritance...
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