Chapter 13- PowerPoint Flashcards
Where is lamin A located?
inner surface of nuclear envelope/membrane
What did Mickey Hayes and Fransie Geringer have?
progeria
What is progeria?
genetic disease that causes premature aging
What causers progeria?
error in lamin A
What does lamin A do?
reinforces the inner surface of the nuclear envelope in animal cells
What is the average life expectancy of someone with progeria?
13 yrs
What was cultivated by Thomas Hunt Morgan at Columbia University in 1909?
Drosophila melanogaster
What happened in the “Fly room”?
Thomas Hunt Morgan made important discoveries in genetics, including sex-linked genes and sex linkage
What organism has contributed to many important biological studies?
fruit flies
What was Thomas Hunt Morgan’s experiment?
crossed a true-breeding fruit fly with normal red eyes and normal wings (pr+pr+vg+vg+) with a fly with recessive purple eyes and vestigial wings (prprvgvg).
What were the results of Thomas Hunt Morgan’s experiment?
high number of parental phenotypes and a low number of recombinant phenotypes.
What is the significance of Thomas Hunt Morgan’s experiment?
pr and vg are physically associated on the same chromosome and that the behavior of these linked genes is due to chromosome recombination.
What is genetic recombination?
process in which two homologous chromosomes exchange segments with each other by crossing- over during meiosis.
What is the frequency of recombination a function of?
distance between linked genes
What does the closer two genes are to each other mean?
the greater the chance they will be inherited together
What is recombination frequency?
the percentage of testcross progeny that are recombinants.
What is a recombinant?
genes not identical to a testcross in any of the parents
What is a linkage map?
map of a chromosome showing relative locations of genes.
tells you location of genes on a chromosome
What is a map unit (mu) or centimorgan (cM) is equivalent to?
recombination frequency of 1%
What is progeny?
offspring
Genes that are widely separated on a chromosome are so likely to?
undergo recombination that no linkage is detected between them – the genes assort independently.
Can Linkage between such widely separated genes can still be detected? if so how?
yes, by testing their linkage to one or more genes
that lie between them.
Do some of the genes Mendel studied assort independently, even though they are on the same chromosome?
yes
What are the most common modes of inheritance? (3)
Autosomal recessive
Autosomal dominant
X-linked recessive
How many pair of autosomes do humans have?
22 paris
How many pairs of sex chromosomes do humans have?
1 pair
What is pedigree analysis used for?
track inheritance patterns in families
What is an example of a dominant pedigree?
juvenile glaucoma
What is juvenile glaucoma? When does this trait occur?
- Disease causes degeneration of optic nerve leading to blindness
- Dominant trait appears in every generation
What should you keep your eye pressure below?
19
In autosomal dominate inheritance what occurs? (3)
- Heterozygotes exhibit the affected phenotype. - Males and females are equally affected and may transmit the trait. - Affected phenotype does not skip generation.
What disease is autosomal dominate inheritance?
achondroplasia
What occurs in autosomal recessive inheritance? (3)
- Heterozygotes carry the recessive allele but exhibit the wildtype phenotype. - Males and females are equally affected and may transmit the trait. - May skip generations.
What disease is autosomal recessive inheritance?
albinism
What is albinism?
pigment melanin is not produced
What is the allele responsible for albinism?
nonfunctional allele of the enzyme tyrosinase
Does albinism affect males and females equally?
yes
Do most affected individuals of albinism have unaffected parents?
yes
What disease is autosomal recessive inheritance?
phenylketonuria (PKU)
What does a double line in a pedigree mean?
mating between first cousins
Where are sex-linked genes located?
sex chromosomes
Which is the homogametic sex?
XX females
Which is the heterogametic sex?
XY males
Are genes inherited differently in males and females?
yes
What does homogametic sex mean?
produce only one type of gamete (X) with respect to the sex chromosomes
What is heterogametic sex?
produce two types of gametes (X and Y) with respect to the sex chromosomes
In duchenne muscular dystrophy what is special about it?
it only affects males, it means that it is an X-linked recessive trait
What type of trait is hereditary enamel hypoplasia?
x-linked dominate trait
Which genders does hereditary enamel hypoplasia effect?
both males and females
Where is the SRY gene is located?
Y chromosome
Where is the SRY gene is located?
Y chromosome
What role does the SRY gene play?
When the SRY gene becomes active, parts of these structures develop as testes
What do the hormones from the testes cause?
tissues for female structures to degenerate and tissues for male structures to develop
In early in embryonic development, are structures that give rise to reproductive organs are the same in XX and XY embryos?
yes
What are chromosomal mutations?
changes in chromosome structure or chromosome number
When does changes in chromosomes structure occur?
when the DNA breaks – the broken fragments may be lost, or attach to the same or different chromosomes
When does changes in chromosomes number occur?
addition or loss of one or more chromosomes, or entire sets of chromosomes
What is deletion?
A segment is lost from a chromosome
What is duplication?
A segment is broken from one chromosome and
inserted into its homolog, adding to the ones already there
What is translocation?
A segment is attached to a different, nonhomologous chromosome
What is inversion?
A segment reattaches to the same chromosome, but
in reversed orientation – the order of genes is reversed
What are aneuploids?
Individuals with extra or missing chromosomes
What are euploids?
individuals with a normal set of chromosomes
What can nondisjunction result in
aneuploids
In humans, what does the addition or loss of an autosomal chromosome generally causes?
embryos will develop abnormally so they
naturally abort
What is Down syndrome?
characterized by short
stature and moderate to severe mental retardation
What is Down syndrome caused by? risk factor?
nondisjunction of chromosome 21, primarily in women, and increases with maternal age
