Transcript UTACCEL 2010

UTACCEL 2010
Adventures in Biotechnology
Graham Cromar
Genetics
Inheritance
Punnett Square
Bb x Bb (Cross)
“B gene” “Big B allele” “Little b allele”
Allele = a form of a gene
Homozygous = BB, bb
Heterozygous (or hybrid) = Bb
B = purple flowers
b = white flowers
1:2:1 Genotypic ratio
3:1 Phenotypic ratio
Segregation and Independent
Assortment
“True breeding”
“Hybrid”
A = Yellow, a = green
B = Round, b = wrinkled
9:3:3:1 phenotypic ratio
Genes are physically on chromosomes
Not all genes assort
independently.
Genes that reside close to one
another on the same
chromosome separate less
frequently and this alters the
characteristic 9:3:3:1 ratio in
predictable ways.
“Linkage”
Three Important Points to Remember
1. Chromosomes are made of DNA
2. Segments of DNA code for a protein
3. Protein in turn, relates to a trait (eye
color, enzymes, hormones..)
DNA Structure
“Twisted ladder”
DNA is a long double-stranded molecule residing
inside the nucleus of every cell. It is usually tightly
coiled forming chromosomes in which it is protected
by proteins.
3’
5’
aatgccgt
ttacggca
5’
3’
Each of the two strands of the DNA molecule is a
chain of smaller molecules. Each link in the chain is
composed of one sugar molecule, one phosphate
molecule and one nucleotide molecule. There are
four types of nucleotides (or 'bases') in the DNA:
adenine (A), thymine (T), guanine (G) and cytosine
(C). The two strands of DNA are structured in such a
way that an adenine on one strand is always
attached to a thymine on the other strand, and the
guanine of one strand is always bound to cytosine on
the other strand. Thus, the two strands of the DNA
molecule are mirror-images of each other.
“complimentary”
“anti-parallel”
Replication
“template”
AT
TA
CG
CG
CG
GC
AT
TA
GC
CG
CG
GC
AT
TA
GC
CG
CG
GC
AT
TA
GC
CG
CG
GC
AT
TA
CG
CG
CG
GC
AT
TA
CG
CG
CG
GC
A
a
a
a
A
A
A : T “Complimentary base pairing”
G: C
Highly recommended:
http://www.scq.ubc.ca/breakfast-of-champions-does-replication/
Mitosis and Meiosis
Aa
Aa
AAaa
AAaa
Aa
Aa
Aa
Aa
A
A
a
a
Gene Expression
How are Proteins Synthesized from DNA
1. DNA is transcribed into mRNA (messenger RNA)
2. mRNA leaves the nucleus and travels to the cytoplasm
3. Ribosomes in the cytoplasm use the code on mRNA to translate it into amino acids
4. Amino acids form a chain - a protein
Transcription and Translation
“Codon”
“Anti-codon”
“Amino acid”
“Transfer RNA”
The Genetic Code
Mutations
Large scale changes
occurring at the level
of the chromosome
also occur. These
change the copy
number of a gene or
genes. Usually this is
bad.
Model Organisms
Advantages:
Idea:
•Fast generation time
•Genetically tractable
•Easy to perform crosses
•Large numbers or progeny
•Interesting features e.g. Frog
morphogenesis
•Plant photosynthesis
•Representative of diverse
lineages
•Similar to ourselves
(mammals)
•Extensive knowledge base
By understanding the function of a gene in one organism, scientists can get an
idea of what function that gene may perform in a more complex organism such as
humans. The knowledge gained can then be applied to various fields such as
medicine, biological engineering and forensics.
ABO blood groups
Blood type is controlled by a gene “i”
There are three forms:
iA iB iO
Each allele makes a
different antigen, a
protein sitting on the
surface of the red blood
cell
iA and iB are co-dominant
iO is recessive
Quiz
1. Draw the complimentary strand to the following single-stranded DNA molecule.
5’
ATTAGGACTTAGGA
3’
2. Three new born babies have been mixed up by the nurses at the hospital. Given
the blood types of the parents and babies can you match the babies to the
correct set of parents?
Parents
AB x O
Babies
AB
A x B
B
AB x AB
O