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Biology unit

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Emma van Leeuwen

on 21 October 2016

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Transcript of Biology unit

L1: DNA
DNA: Deoxyribonucleic acid
"Double Helix"
Bases:
Human Karyotype
made of DNA & Protien
humans: 23 pairs (46 total)
Found in nucleus of cells
Chromosomes replicating and about to split
NB:
Sperm & egg cells contain 23
Red blood cells have no nucleus
(-> no chromosomes)
Genes
L2: making new cells
This lesson stop at DNA and do activity modelling it
Next lesson: prac extracting DNA
Next lesson: chromosomes and worksheet matching karyotypes
Pairs of
autosomes
are
homologous
same length
centromere in same position
genes in same position
Sex chromosomes
1-22
Autosomes
Replication
Cell division
Mitosis:
An identical copy made
(growth and repair)
Meiosis:
calls have 23 chromosomes
(half of parent cell)
produces gametes
(egg and sperm cells)
Replication & transcription (ask Martin)
Next lesson: Mitosis
PRAC: observing mitosis pg 17
Next lesson: Meiosis
PRAC: observing meiosis pg 17
Asexual reproduction
Sexual Reproduction
-> genetic variation
4 possible combinations for gametes
Homologous pairs have genes in the same place BUT the genes may carry different instructions for the same thing....
Different versions of the same gene:
alleles

L3: Characteristics and inheritance
!!?
Recall:
homologous pairs of chromosomes?
genes?
alleles?
Alleles:
Dominant:
will be observed if present
Recessive:
only observed if only allele present
Terms:
Genotype:
the genetic information
Phenotype:
observable characteristics
punet sqrs activity (either martin, PS workbook, monsters inc.
Next: PRAC beetles
Next: dihybrid crosses

Incomplete dominance
Co dominance
Both alleles upper case (eg W, R)
heterozygous -> blend
Heterozygous -> both represented
Dihybrid cross
L4: Pedigrees & disease
As per M
Modeling DNA
1) Transcription
Gene expression
Making new cells
2) Translation
Manufacturing of amino acid chain
Making mRNA
(aka the making of proteins)
Construct this pedigree
Can you work out the genotypes for each individual?
family tree – EYE COLOUR
Colin
Emily
Anne
Paul
Alison
Kylie
Alan
Natasha
James
Scott
Jean
Jim
Did yours look like this?
Susan
can skip a generation
Autosomal Recessive
Key features
X-Linked Recessive
Bb
Bb
Bb
Bb
Bb
Bb
bb
bb
bb
bb
bb
family tree – EYE COLOUR
Key Features
X-Linked Dominant (rare)
Autosomal Dominant
Apart from the 5 blue-eyed individuals, there are at least 8 brown-eyed people with known genotypes, label them.
Is this genetic pedigree possible, if so, explain how
Bb
Bb
Bb
Bb
Bb
Bb
Bb
Bb
bb
bb
bb
bb
bb
8
7
6
5
Yes it is! known genotypes are shown below
3
4
2
1
Key Features
Cannot
skip a generation
Key features
affectedes usually male
Alan
Alan
Vitamin D resistant rickets
Male pattern baldness
Inheritance & Pedigrees
part 1: Transcription
part 2: Translation
Meiosis
Human Karyotype
Chromosomes replicating and about to split
Sex chromosomes
1-22
Autosomes
Genes
Pairs of
autosomes
are
homologous

same length
centromere in same position
genes in same position
Code for same characteristic... but doesn't have to be the same instruction!
So... what colour eyes do you end up with??
Bb
End of Genetics!! ....
... back to evolution
Genetic diseases and modes of inheritance
X-linked inheritance
Eg. colour blindness is X-linked recessive
Females are XX and Males are XY

Affected allele – X
Unaffected allele - X
Difference in how it effects males and females
n
N
X-linked recessive
X-linked dominant
Autosomal recessive diseases
Autosomal dominant diseases
x-linked recessive
Does your pedigree look like this?
Autosomal (found on autosomes)
The code for a particular characteristic
Chromosome from mum
Chromosome from dad
2 of each chromosome:
one set from the mother, one from the father
one of each pair from the mother, the other from the father

Chromosome from mum
Chromosome from dad
Homozygous
Homozygous
Heterozygous
Alleles
So... what eye colour do we end up with?
Dominant:

will be observed (upper case)
Recessive:

only observed if present in
both genes (lower case)

Genotype: BB
Phenotype: brown eyes
Genotype: bb
Phenotype: blue eyes
(b)
(B)
Genotype: Bb
Phenotype: Brown eyes
Yellow Round
yy RR, yyRr
Green Round
YY RR, YY Rr, Yy RR, Yy Rr
Green Wrinkly
Yellow Wrinkly
Yellow (Y) is dominant to green (y)
Round (R) is dominant to wrinkly (r)
Possible genotypes?
yy rr
YY rr, Yy rr
Dihybrid crosses
Look at two pairs of autosomes:
Allele for green coloured skin
Allele for yellow coloured skin
Allele for round skin
Allele for wrinkly skin
4 possible combinations for gametes
X = affected allel
n
N
X = unaffected allel
XX = female
XY = male
Affected female
Homozygous
normal female
Unaffected carrier female
Affected male
Homozygous
normal male
Unaffected carrier male
X X
n n
X X
N N
X X
N n
X Y
n
X Y
N
http://tinyurl.com/84kvz8p
Hydra
Bdelloids
New Mexico whiptail
Parthenogenetic Species:
All female populations
Reproduces by cloning - its eggs require no fertilization, and its offspring are exact and complete genetic duplicates of the mother.

Genetic variation from ingesting DNA of other simple creatures
Hermaphroditic Species
have both male and female reproductive organs
NB: not used to describe ambiguous genitalia in gonochoristic species (eg: humans). Term for that is intersex.
Sequential hermaphrodites:
born as one sex, but can later change into the opposite sex

Simultaneous hermaphrodites:
adult organism that has both male and female sexual organs at the same time

(self-fertilisation does not usually occur)
Clownfish: Start off male, the largest in a group becomes female
Most species of Parrotfish start life as females and later change into males.
Flatworms penis fencing!
Turbellarians mating by penis fencing. Each has two penises on the undersides of their heads which they use to inject sperm through pores in the skin.
The mating ritual involves a violent battle during which two hermaphroditic flatworms attempt to pierce the skin of one another with one of their penises. One organism will inseminate the other; this flatworm becomes the father. The sperm is absorbed through pores in the skin, causing fertilization in the second, who becomes the mother.
Mating Helix aspersa (garden snails).
up to 10 percent of the active genes in microscopic bdelloids comes from bacteria and other organisms like fungi and algae.
Asexual animals can evolve and mutate over time,
but usually do not diversify or last long.
However, records of the bdelloid rotifers show they have been around for more than 40 million years (80 according to livescience) and they have evolved into hundreds of species individually adapted the their environments allowing some to now live in hot springs or the Antarctic waters

doesn't work on ipads :-(
Test
Know glossary
Composition of DNA
Human karyotype and sex determination
Transcription/translation/replication basic
* complimentary mRNA strands
Mitosis/Meiosis basic knowledge (don't need IPMAT)
* what sort of cells
* how many chromosomes
Dominant/recessive
* punnet sqrs mono & dihybrid
Autosomal & X-linked pedigrees

X-linked (found on X-chromosome)
Sickle Cell Anaemia
-> two normal individuals can have an affected child
males/females equal chance of being affected
Huntington's disease
-> two normal individuals
cannot
have an affected child
homozygous affecteds rare
-> all offspring affected = short lineage
male/female equal chance of being affected
frequently skips a generation
sons of an affected female = affected
daughters of an affected male = carriers
X-linked dominant
Affects both male and female however affected males are typically more severely affected
Cannot
skip a generation
Rare as affected male = affected daughters
Does your pedigree look like this?
Construct this pedigree
Reproduction in Animals
External...
or Internal
sperm meets egg
inside
the female's body. Typical of:
most land animals
some fish
sperm meets egg
outside
the female's body. Typical of:
aquatic animals (fish/frogs)
insects
amphibians
Fertilisation can be:
External...
fetus development can be:
Or internal
fish, birds, reptiles, insects
Most mammals
Other ways or reproducing
Sexual reproduction
Full transcript