Download Lecture 3A3 - Ms. RR Wingerden

The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
Big Idea 3: Genetics and
Information Transfer
Heritable information provides for
continuity of life. (3.A.3)
a. Rules of probability can be applied to analyze passage
of single gene traits from parent to offspring.
• The multiplication rule.
To
determine the probability that two or
more independent events will occur
together in some specific
combination, you multiply the
probability of one event by the
probability of the other event.
• The addition rule.
The
probability that any one of two
or more mutually exclusive
events will occur is calculated
by adding their individual
probabilities.
Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Pearson Education, Inc., publishing as Person Benjamin Cummings
College Board, AP Biology Curriculum Framework 2012-2013
14.1-14.4, 15.1-15.5
Copyright © Rebecca Rehder Wingerden
Segregation of alleles and fertilization as chance events. When a heterozygous (Rr) forms gametes,
whether a particular gamete ends up with an R or an r it is like the toss of a coin. We can determine the
probability for any genotype among the offspring of two heterozygous by multiplying together the individual
probabilities of an egg and sperm having a particulate allele (R or r in this example).
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
b. Segregation and
independent
assortment of
chromosomes
result in genetic
variation and can
be applied to
genes that are
on different
chromosomes.
Each true-breeding plant of the parental generation
has identical alleles, PP or pp
Gametes (circles) each contain only one allele for
the flower-color gene. In this case, every gamete
produced by one parent has the same allele.
Union of parental gametes produces F1 hybrids
having a Pp combination. Because the purple-flower
allele is dominant, all these hybrids have purple
flowers.
When the hybrid plants produce gametes, the two
alleles segregate. Half of the gametes receive the P
allele and the other half the p allele.
The box, a Punnett square, shows all possible
combination of alleles in offspring that result from an
F1 x F1 (Pp xPp) cross. Each square represents an
equally probable product of fertilization. For example,
the bottom left box show the genetic combination
resulting form a
egg fertilized by a
sperm.
Alleles, alternative versions of a gene. A somatic cell has two copies of each chromosome (forming
a homologous pair) and thus two alleles of each gene, which may be identical (homozygous) or different
(heterozygous). This figure depicts a homologous pair of chromosomes in an F1 hybrid pea plant. The
chromosome with an allele for purple flowers was inherited from one parent, and that with an allele for
white flowers from the other parent.
Random combination of gametes results in the 3:1
ratio that Mendel observed in the F2 generation
Mendel’s law of segregation. Mendel’s model for inheritance of the alleles of a single gene.
Copyright © 2012 Rebecca Rehder Wingerden
Copyright © 2012 Rebecca Rehder Wingerden
P Generation Starting with two true-breeding
pea plants (YYRR x yyrr).
F1 Generation All plants produce yellow-round
seeds (YyRy).
F2 Generation Produce phenotypic ration of
9:3:3:1
The chromosomal basis of Mendel’s
laws. Here we correlate the results of one
of Mendel’s dihybrid crosses with the
behavior of chromosomes during meiosis.
The arrangement of chromosome at
metaphase I of meiosis and their
movement during anaphase I account for
the segregation and independent
assortment of the alleles for see color and
shape. Each cell that undergoes meiosis in
an F1 plant produces two kinds of gametes.
If we count the results for all cells, however,
each F1 plant produces equal numbers of
all four kinds of gametes because the
alternative chromosome arrangements at
metaphase I are equally likely.
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
1. Genes that are adjacent and close to each other on the
same chromosome tend to move as a unit (linked) and
they do NOT follow Mendel’s law of independent
assortment.
How linkage affects inheritance. A test crosses that Morgan preformed produced a much higher proportion
of parental phenotypes than would be expected if the two genes assorted independently. Based on these
result, he concluded that body color and wing size are usually inherited together in specific combination (the
parental combinations) because the genes for these characters are on the same chromosome.
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
How does linkage between two genes
affect inheritance of characters? Morgan
wanted to know whether the genes for body
color and wing size were on the same
chromosome, and if so, how this affected
their inheritance. The alleles of body color
are b+ (gray) and b (black), and those for
wing size are vg+ (normal) and vg
(vestigial).
2. The recombination (crossing over) of linked genes is a
function of the distance between them.
Design. P Generation was a cross
between true-breeding wild-type (b+ b+ vg
+ vg+) flies with black, vestigial-winged (b
b vg vg) flies to produce heterozygous F1
dihybrids (b+ b vg+ vg) all of which are
wild-type in appearance. Then crossed
the wild-type F1 (b+ b vg+ vg) with the
vestigial-winged (b b vg vg) to produce the
F2 results.
Conclusion. Since most offspring had a
parental phenotype, Morgan concluded that
the genes for body color and wing size are
located on the same chromosome.
However, the production of a relatively
small number of offspring with non-prenatal
phenotypes (recombinants) indicated that
some mechanism occasionally breaks the
linkage between specific alleles of genes
on the same chromosome.
A partial genetic (linkage) map of a Drosophila chromosome. The simplified map shows just a
few of the genes that have been mapped on Drosophila chromosome II. The number at each gene
locus indicates the number of map units between that locus and the locus for arista length (left).
Copyright © 2012 Rebecca Rehder Wingerden
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
3. The pattern of inheritance can often be predicted from
data that gives the parent genotype/phenotype and/or the
offspring phenotypes/genotypes.
• monohybrid:
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
• dihybrid:
YyRr x YyRr
Pp x Pp
Copyright © 2012 Rebecca Rehder Wingerden
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
• sex-linked
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
c. Certain human genetic disorders can be attributed to the
inheritance of single gene traits or specific chromosomal
changes, such as nondisjunction.
Huntington’s disease- lethal dominant allele caused by a
genetic mutation in a gene on chromosome 4. The defect causes
a part of DNA, called a CAG repeat, to occur many more times
than it is supposed to. Normally, this section of DNA is repeated
10 to 28 times. But in persons with Huntington’s disease, it is
repeated 36 to 120 times.
A color-blind father will transmit
the mutant allele to all daughters
but to no sons. when the mother
is a dominant homozygote, the
daughters will have the normal
phenotype by will be carriers of
the mutation.
If a carrier mates with a male
who has normal color vision,
there is a 50% chance that each
daughter will be a carrier like her
mother and a 50% chance that
each sone will have the disorder.
In a carrier mates with a color-blind
male, there is a 50% chance that
each child born to them will have
the disorder, regardless of sex.
Daughters who have normal color
vision will be carriers whereas
males who have normal color vision
will be free of the recessive allele.
The transmission of sex-linked recessive traits. In this diagram, color blindness
is used as an example. The superscript N represents the dominant allele for normal
color vision carried on the X chromosome, and the superscript n represents the
recessive allele, which has a mutation causing color blindness.
Copyright © 2012 Rebecca Rehder Wingerden
As the gene is passed down through families,
the number of repeats tend to get larger. The
larger the number of repeats, the greater your
chance of developing symptoms at an earlier
age. Therefore, as the disease is passed along
in families, symptoms develop at younger and
younger ages.
The disease destroys cells in the basal ganglia,
the part of the brain that controls movement,
emotion, and cognitive ability.
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
c. Certain human genetic disorders can be attributed to the
inheritance of single gene traits or specific chromosomal
changes, such as nondisjunction.
d. Many ethical, social and medical issues surround
human genetic disorders.
• Reproduction issues
• Privacy issues
• Civic issues such as ownership
of genetic information
Trisomy 21/ Down syndrome- is a developmental
disorder caused by an extra copy of chromosome
21. Having and extra copy of this chromosome
means that each gene may be producing more
protein product than normal.
Down syndrome is typically caused by what is called
nondisjunction. If a pair of number 21 chromosomes
fails to separate during the formation of an egg (or
sperm), then this is referred to as nondisjunction.
When that egg unites with a normal sperm to form
an embryo, that embryo ends up with three copies
of chromosome 21 instead of the normal two. The
extra chromosome is then copied in every cell of the
baby's body.
-
HeLa cells have been used extensively in medicine
and heath research.
For example, they were used to test the first polio
vaccine in the 1950s, used for research into cancer,
AIDS, the effects of radiation and toxic substances,
gene mapping, and many other scientific pursuits.
More than 60,000 scientific articles have been
published about research done on HeLa, and that
number is increasing at a rate of more than 300
papers each month.
BBC - The Undead Henrietta Lacks And Her Immortal Dynasty (58:00 min.)
http://www.bbc.co.uk/blogs/adamcurtis/2010/06/the_undead_henrietta_lacks_and.html
Book - The Immortal Life of Henrietta Lacks (3:00 min.)
http://rebeccaskloot.com/the-immortal-life/
Copyright © 2012 Rebecca Rehder Wingerden
Copyright © 2012 Rebecca Rehder Wingerden
The chromosomal basis of inheritance provides an understanding of the
pattern of passage (transmission) of genes from parent to offspring. (3.A.3)
Bozeman Biology: Mendelian Genetics (15:00 min.)
http://www.bozemanscience.com/029-mendelian-genetics
Bozeman Biology: Probability in Genetics (11:00 min.)
http://www.bozemanscience.com/probability-in-genetics
Bozeman Biology: A Beginner’s Guide to Punnett Squares (13:00 min.)
http://www.bozemanscience.com/beginners-guide-to-punnett-squares
Bozeman Biology: Chromosomal Genetics (15:00 min.)
http://www.bozemanscience.com/chromosomal-genetics
Bozeman Biology: Advanced Genetics (13:00 min.)
http://www.youtube.com/watch?v=YoEgUqHOcbc
Bozeman Biology: Linked Genes (18:00 min.)
https://paul-andersen.squarespace.com/linked-genes
Bozeman Biology: AP Genetics Review (20:00 min.)
http://www.bozemanscience.com/ap-genetics-review
Copyright © 2012 Rebecca Rehder Wingerden
Henrietta Lacks (August 1,
1920 - October 4, 1951)
Unwitting source of cells from
her cancerous tumor which
were cultured by Goerge Otto
Gey to create an immortal cell
line for medical research
known as the HeLa cell line.