Bio Chapter 7
What are the steps of gene therapy?
1) Cells are removed from the patient. 2) In the laboratory, a virus is altered so that it is no longer disease-causing. 3) A healthy copy of the patient's missing or damaged gene is inserted into the virus. 4) The virus is mixed with the patient cells. 5) The cells integrate then new gene into their genomes. 6) The genetically altered cells are injected back into the patient. 7) Thanks to the new gene, these cells now produce the desired protein.
How many gene loci does the X chromosome carry?
1,180
How many pairs of autosomes do humans have?
22
There are ___different gene pairs at ___ different loci.
3, 3
How many gene loci does the Y chromosome carry?
60
What is the percent probability that two carrier parents will produce a child with two copies of the recessive allele in their genotype? This is displayed in their phenotype.
A 25% chance
What does it mean when duplication occurs in a chromosome structure?
A chromosome becomes longer after acquiring an extra copy of one of its chromosome segments.
What is a genetic disorder?
A disease caused by an inherited mutation in a gene that is passed down from a parent to a child.
What is a pedigree?
A graph that displays patterns of inheritance.
What is a Karyotype?
A picture of a cell's chromosomes during meiosis that have been sorted and matched in pairs.
What does it mean when deletion occurs in a chromosome structure?
A segment breaks off and is lost from the chromosome.
What does it mean when inversion occurs in a chromosome structure?
A segment breaks off and is reattached in reverse order.
What does it mean when translocation occurs in a chromosome structure?
A segment breaks off of one chromosome and becomes attached to a different, non homologous chromosome.
What are the letters for homozygous dominant?
AA
What is being attempted during gene therapy?
Actively attempting to correct defective genes using genetic engineering.
What do filled symbols (red here) represent?
Affected individuals.
Boys will inherit what chromosome from mom and dad?
An X from mom and a Y from dad.
Girls will inherit what chromosome from mom and dad?
An X from mom and an X from dad.
What occurs when XY individuals SRY gene fails?
Androgen Insensitivity Syndrom (AIS) occurs. Thought they are genetically male, they are physically female.
What are parents with Aa considered carriers of?
Carriers of the recessive allele.
When SRY is present what does it cause some autosomes to do?
Causes genes on some autosomes to produce male characteristics.
What are the letters for heterozygous?
Cc
People with cri du chat syndrome are born with a deletion of what chromosome?
Chromosome 5
What chromosome does the sperm from the male parent contribute?
Contributes either an X or a Y
What do Roman numerals identify on a pedigree?
Different generations.
What do dominant traits need in order to appear in the phenotype?
Dominant traits only need one copy of the dominant allele in the genotype to appear in the phenotype (AA or Aa)
When the SRY is absent what do autosomal genes produce?
Female characteristics (thus female is the default sex in humans)
What do circles represent on a pedigree?
Females.
What is true about treating genetic disorders?
Few genetic disorders have cures.
What are sex linked genes?
Genes that are found solely on the X or Y chromosome.
What do the numbers listed below the symbols identify?
Individuals of a given generation.
What is Achondroplasia?
It is a form of dwarfism, which is caused by a mutation in a gene involved in bone growth.
What type of disease is Cystic Fibrosis?
It is a recessive autosomal disease.
How does Huntington disease develop?
It is causes by dying brain cells.
What does it mean if a trait is X-linked?
It is far more likely to be seen in males.
Where is the gene that causes WAS located?
It is located on the X chromosome and is called WAS.
What is the SRY gene (Sex-determining Region of Y)?
It is the "master sex switch" that determines that the growing embryo will be male. Otherwise it remains female.
What do squares represent on a pedigree?
Males.
In a pair of homologous chromosomes, what does the offspring inherit?
One chromosome is inherited from the male parent, and the other from the female parent.
How many copies of the dominant allele are needed in order for a dominant genetic disorder to be present?
Only one copy of the dominant allele is needed.
What are autosomes?
Paired homologous chromosomes, alike in length, shape, and loci of genetic traits.
Are dominant genetic disorders common or rare?
Rare.
Most sex-linked disorders are the result of what?
Recessive alleles and therefore need two copies to display.
What do recessive traits need in order to appear in the phenotype?
Recessive traits need two copies of the recessive allele in the genotype in order to appear in the phenotype (aa).
WAS mutations is typical for many what?
Sex-linked disorders.
Why are dominant genetic disorders rare?
Since these always present early and are often serious, individuals with them may not live long enough to either reach adolescence or reproduce.
What is a risk of gene therapy for WAS?
Sometimes other blood disorders may occur from the virus that is used to inject the corrected gene into unhealthy cells.
Any increase or decrease in the number of chromosomes almost invariably results in what?
Spontaneous abortion of the fetus, which is estimated to occur in up to 20% of all pregnancies. (Down Syndrome is an exception)
What is being hoped for during gene therapy?
That the corrected cells will produce the needed protein in order to correct the defective genes.
Parents with Aa in their genotype display what?
The dominant allele in their phenotype.
What is a genetic locus?
The location of a particular gene on a chromosome.
What does locus (plural "loci") represent?
The location of a physical gene on a chromosome.
What is genetic engineering?
The permanent introduction of one or more genes into a cell tissue or organ.
What happened in order to cause people to be born with Down Syndrome?
They are born with an extra copy of chromosome 21.
What do WAS mutations cause?
They cause multiple immune system disorders b/c abc and wbc develop from same progenitor cells in bone marrow. Also causes Blood disorders, susceptibility to infections, risk of lymphoma (cancer of the lymph nodes)
Since females carry two X chromosomes what happens if they carry the recessive allele?
They display the disorder.
What chromosome do males give their sons?
They give their Y chromosome (never their X).
What is most often involved in the treatment of genetic disorders?
Treatment typically involves controlling symptoms.
How many copies of each chromosome do you have?
Two
At each genetic locus, what does each individual have?
Two alleles, one on each homologous chromosome.
What are sex chromosomes?
Two chromosomes that determine gender; males have one X and one Y, females have two X's
What do open symbols (blue here) represent?
Unaffected individuals
What are the symptoms of Huntington Disease?
Uncontrolled movements and loss of intellectual faculties.
What does WAS code for?
WAS codes for a protein crucial for healthy blood and immune cells.
What chromosome does the egg from the female parent contribute?
X
What are the letters for homozygous recessive?
bb
