Download Blue eyes

Reproduction
Year 10
What is the purpose of
reproduction?
To pass on genetic material
which will ensure the
survival of the species
Reproduction
• 2 types:
• Asexual Reproduction
– Budding
– Binary Fission (‘split in two’ as
in bacteria)
– Use of a ‘host’ cell (as in
viruses)
– Spores
– Vegetative (cutting, rhizomes)
• Sexual Reproduction
– Seed Formation by way of
Pollen and Egg fusion
Puffball
Asexual Reproduction
• All offspring are identical (clones)
Advantage
– Quick population growth
– No partner needed
– Logging trunks straight, bananas
no seeds
Disadvantage
– Kill one, kill all
•Strawberry runners
•Potato tubers
•Cooch grass rhizome
•Aphids
• Human intervention – cuttings, genetic engineering
Sexual Reproduction
• Offspring are different from parents (variation)
Advantage
– Survival of the fittest (finches)
– If environmental change occurs, increased chance of
species survival.
Disadvantage
– Need a partner!?
– Energy wastage
The Structure of DNA
• DNA
(deoxyribonucleic
acid) is the genetic
material found in the
nucleus of living cells
• Its structure is
described as a double
helix
Animation of DNA in the body
Chromosomes
• DNA is divided into
“chunks” called
Chromosomes
• Humans have 23
pairs of chromosomes
• Why?
• 1 from Mum, 1 from
Dad
• XX pair is a female
• XY pair is a male
• Karyotype diagram
Genes
• Each chromosome is
divided up into
genes.
• Genes are a
sequence of DNA that
codes for a trait, such
as fixed or free
earlobes.
• Alleles are alternative
forms of the same
gene
Sometimes the appearance can be
enhanced by other means…
Gametes
• Gametes (sex cells) only have
23 single chromosomes.
Why?
• During fertilisation the egg
and sperm come together to
give a new cell with 23 pairs of
chromosomes.
Gametes
• A gamete is a single cell, one
from each parent, that creates
a new individual
• Female gamete is known as
an ovum or egg
• Male gamete is known as a
sperm
• Each human gamete has 23
chromosomes
• All other cells in your body
have 46 chromosomes.
• When the egg and sperm
fuse, a new life is produced,
having all 46 chromosomes
Fertilisation
• This is the process when the
chromosomes of the egg and
sperm combine, creating a new
individual
• Fertilisation may occur inside
the animal or in the
environment (water)
• The single cell organism
(zygote) starts to divide into an
embryo then a foetus
• Nine months is required for the
foetus to develop into a fully
developed newborn baby
Male reproductive Organs
• Penis
– Insertion of semen
• Urethra
– Tube expelling sperm and urine
• Scrotum
– Temp. regulation
• Testes
– Make sperm and testosterone
• Vas deferens
– Transports sperm
• Seminal vesicle
– Produce fluid to help motility of
sperm
Female reproductive organs
• Vagina
– Birth canal
• Cervix
– Allows passage of sperm and
menstrual blood
• Uterus
– Egg implantation site
– Expands to hold baby
• Ovary
– Produces eggs and hormones
• Fallopian tube
– Allows passage of egg
– Site of conception
Menstrual Cycle
• Once a month an egg leaves the ovaries (ovulation)
• travels down the fallopian tubes towards the uterus
• Before ovulation Oestrogen stimulates the uterus lining
to build up in preparation for pregnancy
• If the egg is fertilized by a sperm it attaches to the wall of
the uterus and develops into a baby.
• If the egg isn't fertilized it doesn't attach to the wall so the
uterus sheds the extra lining.
• The blood and unfertilized egg leave the uterus through
the vagina. This is a menstrual period.
Menstrual Cycle
• Hormones are the chemical messengers
which co-ordinate the 28 day cycle
Changes during puberty
• Hormonal changes cause:
–
–
–
–
–
–
–
Growth spurt
Hair growth
Body shape changes
Voice changes
Menstruation begins
Body odour
Emotions fluctuate
Amphibian life cycle
• Create a poster which
explains the life cycle of a
frog.
• Groups of 4 (think about
the make up of your team
not just friends!)
• Marked on teamwork
• Informative resources
• Presentation
• Timescale?
amphibian
Alleles
• Every body cell has 23 pairs of
chromosomes. WHY?
• During fertilisation one came from Mums
egg and one from Dads sperm
• So each cell must have a pair of genes,
called alleles, coding for every trait.
• They may be the same e.g AA
• Or different e.g. Aa
Alleles – alternative forms of the same gene
• Alleles are assigned letters to distinguish one
from another e.g. Tongue roll alleles T or t.
• Alleles may be dominant or recessive
depending on whether the trait is seen.
• Recessive
– blue eyes
– Small letter
• Dominant
– hitchhikers thumb, tongue roll
– Capital letter
• The characteristics displayed are known as
phenotype.
Alleles
• Genotytpe is the genetic make up of an individual
• E.g. Tongue roll alleles are represented by T or t
• What are the 3 possible genotypes?
– TT, Tt, tt
Genotype
Father
Mother
TT
tt
Phenotype Can roll
Can’t roll
• What is the genotype and phenotype of the
children ?
– Genotype Tt, phenotype can roll
Punnet Square
• All possible combinations
of gametes can be shown
(father can roll TT,
mother can’t tt)
• The genotype of all
offspring can be worked
out
• Can work out the chances
or ratio of any
combination occurring in
this case:
• Genotype 100% Tt
• Phenotype 100% Can roll
Fathers sperm
M
o
t
h
e
r
s
e
g
g
T
T
t
Tt
Tt
t
Tt
Tt
Punnet Square
• What are the Genotypes
of children?
• What are the
phenotypes?
• Roller, non roller
• What is the ratio of
phenotypes?
• 3:1
• How can we tell if the
genotype of a tongue
roller is TT or Tt?
Fathers sperm
M
o
t
h
e
r
s
e
g
g
T
t
T
TT
Tt
t
Tt
tt
GENETICS PROBLEMS
In humans, blue eyes are recessive to brown:
Dad (Blue eyes)
Mum (Brown eyes)
Is Mum homozygous for brown eyes?
Baby (Blue eyes)
________
How do you know? (complete the Punnett square)
MICE
In mice, albino is a recessive trait
Big Momma mouse
Poppa mouse
Stuart Little
Complete the Punnett square to show how Stuart ended up an
albino
If there were 8 babies in the litter, how
many would we expect to have normal
colouring? _________
LABRADORS
In Labs, black is the dominant trait
The pups are all black
These 2 are mated
What is the genotype of the pups? _____________
The pups grow up and 2 are mated
Here are their kids…
Show how this came about
(draw the Punnett square)
What percentage would we expect to have golden colouring? ____________
Eye colour
In eye colour the brown eye allele is dominant, so we call it
B, and the blue eye is recessive, so we call it b:
BB
Bb
bb
Homozygous
brown-eyed
parent
Heterozygous
brown-eyed
parent
Blue-eyed parent
What would the offspring have? – This is an
example of monohybrid inheritance
Eye colour
Example 1: A homozygous
brown-eyed parent and a
blue-eyed parent:
X
BB
Parents:
Example 2: 2 heterozygous
brown-eyed parents
bb
Bb
X
Bb
Gametes:
B
B
b
b
B
b
B
b
Offspring:
Bb
Bb
Bb
Bb
BB
Bb
bB
bb
All offspring have brown eyes
25% chance of blue eyes
Eye colour
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
Bb
bb
B
b
b
b
Bb
Bb
bb
bb
Equal (50%)
chance of
being either
brown eyed or
blue eyed.
Example questions
1) In mice, white fur is dominant. What type of offspring
would you expect from a cross between a heterozygous
individual and one with grey fur? Explain your answer with a
genetic diagram.
2) A homozygous long-tailed cat is crossed with a homozygous
short-tailed cat and produces a litter of 9 long-tailed kittens.
Show the probable offspring which would be produced if two
of these kittens were mated and describe the characteristics
of the offspring (hint: work out the kitten’s genotype first).
DISCRETE HUMAN CHARACTERISTICS
Discrete is “not continuous” – it must be one of a few possibilities.
Possible
Dominant
Dominant
Phenotype
Genotypes
Trait
Gene
Location
Recessive
Phenotype
Recessive
Genotype
color of iris
2
not blue
EE or Ee
blue
ee
widow's peak
4
peak
PP or Pp
no peak
pp
cheek dimples
5
dimples
DD or Dd
not dimples
dd
face freckles
9
freckles
FF or Ff
no freckles
ff
mid-digital hair
10
hair
HH or Hh
no hair
hh
Hitchhiker's
thumb
17
straight
TT or Tt
curved
tt
Hallux length
(toes)
20
long 2nd toe
BB or Bb
long big toe or
bb
= to 2nd toe
ear lobes
21
free
LL or Ll
attached
ll
tongue rolling
22
ability
RR or Rr
no ability
rr
cleft chin
16
cleft
YY or Yy
no cleft
yy