DNA & Genetics
Biology
Remember chromosomes?
• What are genes?
• Made up of DNA and are units of heredity;
unique to everyone
• What are traits?
• Are physical and unseen characteristics.
• Examples:
• physical: color of skin or eyes
• unseen: blood type or intelligence level
Remember chromosomes?
• What are chromosomes?
• Carrier of genetic materials,
thread-like fibers found in
the nucleus
• They are composed of genes
• What is an allele?
• Gene form for each
variation of a trait of an
organism. Example: gene for
height can express tall or
short
DNA structure
• DNA = deoxyribonucleic acid
• A nucleic acid, genetic material
• Carries the code for all proteins that
make up the human body
• Composed of paired nucleotides
• Nucleotides contain a phosphate group,
5-carbon sugar (deoxyribose), and a
nitrogen base
DNA structure
• The 4 nitrogen bases of DNA:
–
–
–
–
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Nucleotide
structures:
1 phosphate
group
1 5-carbon
sugar
1 nitrogen
base
DNA structure
DNA structure
• Structurally pyrimidines pair with
purines
• Thymine (T) and Cytosine (C) are
pyrimidines
• Adenine (A) and Guanine (G) are purines
• Nitrogen bases are held together by
hydrogen bonds
• Guanine (G) pairs with Cytosine (C)
• Adenine (A) pairs with Thymine (T)
DNA structure
• Composed of 2 complementary strands
• Complete the following DNA strand:
• TACGTACCGCAGGTAATC
• ATGCATGGCGTCCATTAG
DNA
What does DNA look like?
• Double helix
• 1st published in
1951
• Credited to
Watson and Crick
• 1st seen by
Rosalind Franklin,
whose pictures
were stolen from
her lab
DNA Replication
•
•
•
•
Process where DNA copies itself
DNA replicates before mitosis
DNA replicates before meiosis I
The 2 strands of a DNA molecule
separate when the hydrogen bonds
break. Two complimentary strands form,
each using one of the single DNA as a
template
DNA Replication
http://video.google.com/videoplay?docid=5595842
121339099106&q=DNA+replication&hl=en
http://video.yahoo.com/video/play?p=DNA+replicat
ion&toggle=1&cop=mss&ei=UTF8&b=2&oid=b4115effae59a11e&rurl=www.biotea
ch.ubc.ca&vdone=http%3A%2F%2Fvideo.yahoo
.com%2Fsearch%2Fvideo%3Fp%3DDNA%2Bre
plication%26toggle%3D1%26cop%3Dmss%26ei
%3DUTF-8
Steps of DNA Replication
• Enzyme breaks hydrogen bonds between
paired nucleotides
• DNA strand unzips
• Free nucleotides move in and bond with
complementary pairs on unzipped strands of
DNA
• Enzyme bonds the newly paired nucleotides
together
• 2 exact copies of the original DNA strand are
produced
Steps of DNA Replication
• Replicate the following DNA strand:
• TACGTACCGCAGGTAATC
ATGCATGGCGTCCATTAG
DNA Replication
RNA structure
•
•
•
•
•
RNA is produced from a DNA strand
What is RNA?
Ribonucleic acid
Consists of 1 strand of nucleotides
RNA nucleotides have 1 phosphate
group, 1 5-carbon sugar (ribose), and 1
nitrogen base
RNA structure
• The 4 nitrogen bases of RNA:
–
–
–
–
Uracil (U)
Cytosine (C)
Adenine (A)
Guanine (G)
RNA structure
• Nitrogen bases are held together by
hydrogen bonds
• Guanine (G) pairs with Cytosine (C)
• Adenine (A) pairs with Uracil (U)
Compare DNA and RNA
•
•
•
•
DNA:
2 strands
Deoxyribose sugar
Phosphate group
4 nitrogen bases:
adenine
thymine
guanine
cytosine
•
•
•
•
RNA:
1 strand
Ribose sugar
Phosphate group
4 nitrogen bases
adenine
uracil
guanine
cytosine
Types of RNA
• Messenger RNA – mRNA: carries sequence of
nucleotides that code for protein from
nucleus to ribosomes
• Transfer RNA – tRNA: picks up individual
amino acids in the cytoplasm & carries them
to the ribosomes
• Ribosomal RNA – rRNA: found in ribosomes,
helps bind mRNA and tRNA together during
translation (protein synthesis)
Transcription: DNA into RNA
• Enzymes break hydrogen bonds in DNA
strands
• Unzipped strand of DNA gets paired
with free RNA nucleotides
• RNA nucleotides bond together
• Enzymes break hydrogen bonds between
DNA and RNA strands.
• RNA strand becomes mRNA and leaves
the nucleus
Transcription: DNA into RNA
mRNA
• Composed of a codons
• A codon is a series of “3” letters or bases
that make up the code of mRNA
• Codons are the “recipe” for making all amino
acids in the body
• Every strand of mRNA starts with the codon
AUG or the start codon – starts protein
synthesis. There is only 1 start codon
• Every strand of mRNA ends with a terminator
or “stop” codon – stops protein synthesis.
There are 3 stop codons.
Translation of mRNA
• Translate the following mRNA into
amino acids using the Universal codon
chart
• AUGAGGGCUCGAUGA
• MET-ARG-GLY-ARG-STOP
Universal codon chart
What does mRNA do?
• Brings the code for protein production and
assembly to the ribosome
• At the ribosome the code in the mRNA is
translated into amino acids
• mRNA codons enter the ribosome
• transfer RNA or tRNA brings the
complementary base pairs or the anti-codon to the ribosome from the cytoplasm
• A protein is produced when the mRNA codon
and the tRNA anti-codon bond
Translation