genetics nicky mulder. life as we know it is specified by genomes they hold all the necessary info...
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Genomes Prokaryotes EukaryotesTRANSCRIPT
Genetics
Nicky Mulder
Life as we know it is specified by
genomes They hold all the necessary info to grow and function
Copyright-Anna Kramvis 2
GenomesProkaryotes
Eukaryotes
History of genetics
1953 Watson and Crick discover structure of the DNA double helix
Mendel’s genetics
Studied inheritance of seed change –characterized dominant and recessive phenotypes
Some genetics concepts
Diploid –two copies of each chromosome Two copies of each gene (allelles), if the
same then homozygous, if different –heterozygous
Alleles can be wild type or mutant Interactions between alleles can be
dominant or recessive
Central Dogma
DNA RNA Protein
Genomes
RNA genomes Some viral genomes are RNA Retrotranscribed into DNA
DNA genomesProkaryotes
Eukaryotes
Composed of nucleic acids
Nucleic Acids -DNA Deoxyribonucleic acid Nuclear material, found in nucleus Double stranded Sugar: 2’-deoxyribose Nucleotides
Adenine (A) Cytosine (C) Guanine (G) Thymine (T)
Copyright-Anna Kramvis 11
Nucleic Acids -RNA Ribonucleic acid Genome of some viruses Found in cytoplasm Single stranded Sugar: ribose Nucleotides
Adenine (A) Cytosine (C) Guanine (G) Uracil (U)
Nucleotides
OOCHCH22
CC
CC CC
CC
HHHH HH
HHOHOH
PP OO
OO
OO--
OO--
5’5’
3’3’ 2’2’
1’1’
basebase
4’4’
PP
OO
OO--
OO--
PP
OO
OO--
OO--
ααββγγ
phosphatephosphate
sugarsugarXX
deoxyribonucleotidesdeoxyribonucleotides
HH
Ribonucleotides Ribonucleotides –extra OH–extra OH
OHOH
pyrimidinepyrimidinepurinepurine
Bases
Copyright-Anna Kramvis 14
From nucleotide to ssDNA
Copyright-Anna Kramvis 15
http://haplogroup-i.com/img/DNA2.gifhttp://haplogroup-i.com/img/DNA2.gif
Sense strand = mRNA
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Base pairing
www.mun.cawww.mun.ca
Hydrogen bonds
AT –weaker bond (2 versus 3 for GC)
Representation of sequences String of letters (ACGT) usually written 5’-
3’
5’-ATGCGTGGCCTAAACGTTCAGGTCGA-3’3’-TACGCACCGGATTTGCAAGTCCAGCT-5’
Reverse complement = reverse strand written 5’ to 3’
Sequence formats: Fasta
> [title]
[sequence]
>example sequenceGGAAAATTAGATGCATGGGAAAAAATTAGGATTAGACAAGATGGGAAACCGCATTA
Sequence formats: GenBank
LOCUS 525-42 1588 bpDEFINITION 525-42 1588 bpTITLE 525-42FEATURES Location/Qualifiers exon 39..70 /note="exon1 is believed to have an alternative splice donor site"ORIGIN
1 ATGTT AAGAG GGGGA AAATT AGATG CATGG GAAAA AATTA GGTTA AGGCC51 AGGGG GAAAG AAATG CTATA NGATA AAACA CCTAG TATGG GCAAG CAGGG101 AGCTG GAAAG ATTTG CACTT AACCC TGGCC TTTTA GAGAC ATCAG ANGGC151 TGTAA ACAAA TAATG NAACA GATAC AACCA GCTCT TCAGA CAGGA ACAGA
DNA structure continued Base pairs stack into a helix Alternating sugars and phosphates form
backbone
www.dkimages.comwww.dkimages.com
Double helix
DNA supercoiling
DNA denaturation Unwinding of the strands and breaking of
base pairs Achieved by heat Denaturation temperature depends on
AT/GC content Required for replication, transcription, etc. DNA can also be degraded by
exonucleases
Copyright-Anna Kramvis 24
Central dogma of molecular biology
http://www.cem.msu.edu/~reusch/VirtualText/nucacids.htmhttp://www.cem.msu.edu/~reusch/VirtualText/nucacids.htm
DNA replication
Copyright-Anna Kramvis 25cellbiology.med.unsw.edu.aucellbiology.med.unsw.edu.au
DNA polymerase can only extend 5’ to 3’. Leading strand is generated normally, lagging strand goes opposite way so is done in ‘Okazaki’ fragments
DNA repair and recombination
DNA polymerases can make mistakes -> mutations
DNA repair mechanisms Recombination can occur –cutting out and
insertion of pieces of DNA These can all leads to changes in genetic
material and thus changes in phenotype!
Base pairing exercise
Copyright-Anna Kramvis 27
1.Determine the complementary strand for the following sequences:
•5’ATGCCATTAGCTTAGCATTGGAAAGTCATGCCATG3’
•5’CATCGGTAACTAGCTAATGGCCTACTGCCATGCCT3’
2. Determine the reverse complement of the strands above. 3. Transcribe the above sequences into RNA.
4. Work out the percent GC content. Which strand will have stronger bonding between the two strands?
Additional questions
Which of these sequences will have the higher denaturation temperature?
1) ATATCATATGATATGTA2) CGGTACTCGCTCAGGT The base composition of a sequence was
determined, there are 20% adenines, what is the % cytosine?