Transcript 1. Revision Powerpoint

Revision Generation Game
Compiled by
Dr ￗ Rat
What do these genetic terms mean?
gene
Section of DNA that codes for a particular trait
or characteristic.
allele
A different form of a gene that codes for a
different version of a characteristic.
genotype
A description of the pair of alleles present
for a characteristic.
phenotype The physical expression of the alleles.
homozygous Pair of alleles that produce a characteristic
that are the same, e.g. HH.
heterozygous Pair of alleles that produce a characteristic
that are different, e.g. Hh.
dominant
An allele that will always be expressed even
when there is only one of these alleles present,
represented by a capital letter.
recessive
An allele that will only be expressed when
both alleles are of this type, represented
by a lower case letter.
Female Reproductive System
A
B
C
D
E
A
B
C
D
E
F
F
A = oviduct B = ovary C = uterus D = cervix E = vagina F = thigh
The male Reproductive System
B
F
A
D
C
E
B
F
A
D
C
E
A = sperm duct
D = testicle
B = urethra (to bladder)
E = scrotum
C = penis
F = gland
NGA WAHANGA O TE PUTIPUTI
Start here,
go clockwise
Stigma
Wahanga
wahine
o te
putiputi
Ovary
Pistil
tohere
hapiapia
riunga
hae
karure
hae
miro
Wahanga
tane
puapua
kohanga
heki
Anther
heki putiputi
rau arai
kakau
Stamen
Filament
Petal
Ovule
Sepal
Stem
RR x rr – crossing homozygous parents
What are the possible offspring of a cross between a
homozygous red flower and a homozygous yellow flower?
Homozygous means that both alleles of a gene are the same.
Red is the dominant allele for these flowers, so the alleles
for petal colour are: red = R , yellow = r.
phenotype:
x
genotype:
RR
rr
RR x rr – F1 offspring
parental genotype:
gametes:
RR
R
x
R
r
r
F1 offspring
genotype:
rr
r
r
R
Rr
Rr
R
Rr
Rr
What are the phenotypes of the F1 offspring?
?
RR x rr – F1 phenotypes
parental genotype:
F1 genotypes:
RR
Rr
x
Rr
rr
Rr
Rr
F1 phenotypes:
(Click twice on the buds
to reveal the flowers;
click again to close them.)
The possible offspring of a cross between two homozygous
parents are always heterozygous and so the dominant
characteristic is always expressed in this generation.
Rr x Rr – crossing heterozygous parents
The offspring (Rr) from the first cross (RR x rr) are called
the F1 generation. What happens in a cross between
these offspring?
Both parent plants are now heterozygous, so the alleles
in each plant are different.
F1 generation
phenotype:
X
genotype:
Rr
Rr
Rr x Rr – F2 offspring
parental genotype:
gametes:
Rr
R
x
r
R
R
F2 offspring
genotype:
Rr
r
r
R
RR
Rr
r
Rr
rr
What are the phenotypes of the F2 offspring?
?
Rr x Rr – F2 phenotypes
parental genotype:
F2 genotypes:
Rr
RR
x
Rr
Rr
Rr
rr
F2 phenotypes:
(Click twice on the buds
to reveal the flowers;
click again to close them.)
In the F2 generation, 3 of the 4 possible offspring are red.
Only one offspring shows the recessive phenotype.
When two heterozygous parents are crossed, the possible
offspring will always show a 3:1 ratio in favour of the
dominant phenotype.