Download powerpoint lesson oedigrees karyotypes

Humans reproduce sexually. This means females
produce eggs (ova) carrying only one of each
chromosome—total 23, while males produce sperm
carrying only one of each—total 23. When sperm and
egg unite at fertilization, a zygote with a full double
set of chromosomes—total 46—is formed.
It’s random which set of your 23 homologous chromosomes you’ll sort
(by cell division called meiosis) to each gamete.
This drawing (organism w/ 2 kinds of chromosomes) shows 2n
combinations of chromosomes possible (n=# different types
chromosomes)in gametes (sperm or eggs).
223 or about 8 million possible ways exist to sort your two sets of
23 chromosomes into gametes!
Meiosis is a type of cell division that results in your giving one
of each chromosome to your child in a sex cell, sperm or egg.
Having one copy of each chromosome is called haploid.
For a child to have the correct amounts of every protein needed for the
complete assembly of its body during development, the zygote must
have received one or every type of chromosomes #1-22 from EACH
parent.
The child must also receive one X chromosome from each parent if a
female (genotype XX, phenotype female). A boy must also receive one
X chromosome from his mother’s egg, but one Y chromosome from his
father’s sperm.
X
X
Diploid 2n karyotype of a female child
X
LE 14-4
Because offspring have 2 of each type of chromosome, they have 2
copies of each gene.
Offspring may receive identical versions of the gene (alleles) from
both parents and be homozygotes OR they may receive different
alleles from the two parents and become heterozygotes.
Allele for purple flowers
Locus for flower-color gene
Allele for white flowers
Homologous
pair of
chromosomes
Only a few genes (see striped ends) are shared on
X and Y chromosomes
Males usually only have one copy
of genes on the X chromosome,
X-linked genes
e.g., XHXh or XHXH girls
XHY or XhY males
So males have X-linked recessive
disorders more often, but
females have X linked dominant
disorders more often.
A map of the human X chromosome
showing some of the X linked recessive
disorders that males inherit more often
(called recessive sex linked diseases)
Genes carry out the jobs of a cell. If critical jobs are done by
a protein, then mutations that alter its function can cause
genetic disorders.
Diabetes—no insulin made (Autosomal recessive—males & females inherit equally)
Tay Sachs –no brain lipid digesting enzyme made (autosomal recessive)
Dwarfism—no growth factor made autosomal (recessive)
Albinism—no pigment for skin, hair, eyes made (autosomal recessive)
Cystic fibrosis—no salt channel made to allow
ions of salt to escape cells recessive (autosomal recessive)
antennepia—legs instead of antennas—autosomal dominant!
Colorblindness, boy in a bubble suit disease, hemophilia—
sex linked recessive—on the X csome in humans
Huntington’s disease—too much Huntington protein—
autosomal dominant, late onset, one of a few dominant and common inherited
disease—inherited in half of children & equally in males & females
Inherited breast cancer—BRCA genes inactive—no tumor suppressors—autosomal
dominant—but since the protein is affected by estrogen hormone, women do end
up with breast cancer more often. Men who inherit it get other cancers more
often.
Certain inherited leukemias—translocation makes cell cycle control genes too active
and too abundant—dominant autosomal.
Traits are the result of activity of proteins coded by
parts of DNA called genes.
Genes come in slightly different versions called
alleles.
Some alleles are dominant. These dominant alleles
code for abundant and active proteins.
Some alleles are recessive. These recessive alleles
code for scarce (very little or none) or inactive
proteins.
For genes on autosomal (not X or Y)
chromsomes, recessive traits are only apparent
in people with two recessive alleles
(homozygous recessive genotype); both parents
must pass a recessive allele.
genotype Dominant autosomal trait phenotype
BB or IBIB keeps hair in adulthood
Bb or IbIb keeps hair in adulthood
genotype recessive autosomal trait phenotype
bb or IbIb bald in adulthood
Pedigrees are family trees showing whether each person does
(filled in) or does not (not filled in) have a particular trait. Males
are shown as □ & females as O.
Ww
ww
ww
Ww
First generation
(grandparents)
Ww
ww ww Ww
WW
or
Ww
Ww
ww
Second generation
(parents plus aunts
and uncles)
Third
generation
(two sisters)
ww
No widow’s peak
Dominant trait (widow’s peak)
Recessive Trait: No Widow’s peak
Cleopatra (Queen of Egypt, descended of the Pharoahs). Since
Pharoahs were considered god-like, they were only able to marry
people of the same status.
2/17/2010, King Tut’s 5 generation pedigree was published
(DNA tests of blood cells in mummies)
Tut’s parents were brother and sister, and
Tut was married to his sister.
King Tut had several obvious disorders,
likely due to double doses of recessive
alleles from his brother/sister parents:
Cleft palate, club foot, severe scoliosis,
other bone disease
Tut’s own two children were still-born.
LE 14-14b
First generation
(grandparents)
Second generation
(parents plus aunts
and uncles)
Ff
FF or Ff ff
Third
generation
(two sisters)
Attached earlobe
Recessive trait (attached earlobe)
Ff
ff
ff
Ff
Ff
ff
FF
or
Ff
Ff
ff
Free earlobe
Pedigree for a disease caused by an autosomal recessive
allele.
Note that marrying a relative increases changes of inheriting 2
recessive alleles.
Pedigree for a disease caused by a
dominant allele. No carriers! One disease
causing allele makes you sick.
Geneticists use pedigrees to locate relatives who are
healthy versus ill due to inherited disease. Comparing
their data allows the defective gene to be identified.
Construct pedigrees for your own family’s trait data. Use the
pedigree to determine as many genotypes (the 2 forms of
the alleles) as possible.
Widow’s peak—dominant—color symbol if person has widow’s peak
ww -no widow’s peak
Ww or WW -has widow’s peak
Attached earlobe—recessive—color person with attached earlobes
EE or Ee-free earlobe
ee-attached earlobe
Hitchhiker’s thumb—recessive—color person who can bend thumb all
the way; half color (a carrier) a person who can bend it a little
HH-stiff thumb (no bend)
Hh -bends a little
hh-up to a 90 degree backward’s thumb!
Tongue rolling—dominant—color person who can roll tongue
TT or Tt-can roll tongue
tt -can’t roll tongue
Curly hair—dominant
cleft chin--dominant
Freckles--dominant
No hair on finger middle bond—recessive
Right over left thumb/hand-recessive
bent pinky-dominant
Punnett Squares allow you to predict all the possible
combinations of gene alleles that mates might pass to
children. Here is an example for a father having one A and
one a allele and a mother having one A and one a allele. By
random chance of which gametes are passed, about ¼ of
their children should have two recessive alleles.
For your traits of tongue rolling, hitchhiker’s thumb,
widow’s peak, and ear attachment, create a Punnett
square for possible allele combinations that you and
one other person in the class might pass to children
if you mated.
Use the Punnett square results to estimate the
fraction of your children who would have each
of the traits.
-----------If you don’t finish in class, finish for homework.
Sample pedigree to do as a class.
Bent finger (dominant trait)
Mom’s side of the family
Great Grandfather
yes
Great Grandmother no
Grandfather
no
Grandmother
yes
Mother
no
Father
yes
Child
no
dad’s side
yes
no
Males usually only have one copy
of genes on the X chromosome,
X-linked genes
e.g., XHXh or XHXH girls
XHY or XhY males
So males have X-linked recessive
disorders more often, but
females have X linked dominant
disorders more often.
Sex linked disorders
Pedigree for a sex linked Dominant
allele
Pedigree for a sex linked recessive
allele
Queen Victoria’s X linked Recessive
Pedigree for Hemophilia
Pedigree for an autosomal
dominant allele