Genetics Nicky Mulder. Life as we know it is specified by genomes They hold all the necessary info...

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)


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


From nucleotide to ssDNA


http://haplogroup-i.com/img/DNA2.gifhttp://haplogroup-i.com/img/DNA2.gif

Sense strand = mRNA


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


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


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?

Genetics Nicky Mulder. Life as we know it is specified by genomes They hold all the necessary info...

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