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38 Cards in this Set

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A chart which shows the relationships within a family is called ____________.
pedigree chart
Why can't some obvious human traits be traced to single genes?
Because many human traits are determined by multiple genes or are influenced by both genetics and environmental factors. For example, both genetics and environment (nutrition and exercise) determine height.
When chromosomes from photographed cells are pairted together by biologists, it is called a __________/
karyotype
Which chromosomes determine an individual's sex?
sex chromosomes
In humans 2 of the 46 chromosomes are sex chromosomes. The remaining 44 chromosomes are called _______________.
autosomal chromosomes or autosomes
Females have two copies of a large _____ chromosome.
X
Males have one ___ and one small ______ chromosome.
X and Y
Why are males and females born in a roughly 50:50 ratio?
Because all human egg cells carry a single X chromosome (23,X). Half of all sperm cells carry an X chromosome and half carry the Y (23,Y) resulting in half of the zygotes being 46,XX and half being 46,XY.
What does the Rh stand for in the Rh blood group?
rhesus monkey where the single gene determining this blood group was discovered.
Why is knowing a person's genetically determined blood group important?
Because receiving a transfusion of the wrong blood type during a medical procedure can be fatal.
What are the two alleles of the Rh blood group gene?
positive and negative
How many alleles are there for the ABO blood group?
Three - I(A), I(B) and i .
A and B are codominant -- resulting in A, B, or AB blood types.
i is recessive ii = Blood type O
If a person has a dominant allele for a genetic disorder, what happens?
The genetic disorder is always expressed.
Achondroplasis (a form of dwarfism)
Huntington's Disease - no symptoms until 30s or older
Name a disease caused by a codominant allele.
sickle cell disease
Name some disorders caused by autosomal recessive alleles.
Tay-Sachs, PKU, cystic fibrosis, Albinism, Galactosemia
Explain how a small change in DNA causes the genetic disorder Cystic Fibrosis.
On chromosome 7 a recessive allele is missing 3 DNA bases which removes one amino acide from a protein. The CTFR protein is responsible for transporting chloride ions and because of the damaged protein tissues in the body malfunction.
How does a DNA change cause the genetic disorder sickle cell disease?
The DNA base substitutes the amino acid valine for glutamic acid. The abnormal hemoglobin is less soluble causing molecules to stick together forming sickled cells.
What is the relationship between sickle cell disease and malaria?
In people who are heterozygous for the sickle cell allele, they are healthy and also are resistant to malaria. In areas of the world where malaria is more common, more people have the sickle cell allele. Since many african americans trace ancestry to west Africa which is a malaria prone region, the sickle cell allele is more common in that population.
Is the sickle cell allele dominant or recessive?
codominant
How many base pairs of DNA are contained in a human diploid cell?
More than 6 billion
How much of chromosomes are made up of genes?
Only about 2 percent
How many bases does a gene have?
the average human gene has about 3000 base pairs
How many base pairs does the largest gene in the human genome have?
More than 2 million
What are the smallest human autosomes?
Chromosomes 21 and 22
Describe the make up of chromosomes 21 and 22.
They both contain genes, some of which are important for human health including some that are related to genetic disorders. Parts of Chromosome 22 contain repetitive DNA that do not code for proteins. Parts of Chromosome 21 have no genes at all.
What are sex linked genes?
Genes located on the X or Y chromosome
Where are the human genes associated with color blindness located?
On the X chromosome
Why is color blindness more common in males than females?
Because males have just on X chromosome so all X-linked alleles are expressed in males even if recessive. To be expressed in females, there must be two copies of the allele, one on each of the two X chromosomes.
Name two other X linked disorders.
Hemophilia and Duchenne Muscular Dystrophy
What happens to the extra X chromosome in females?
One X chromosome is randomly switched off forming a Barr body in the nucleus
If a cat's fur has three colors is it male or female?
It must be female because the X chromosomes control color spots and different X chromosomes were switched off in different parts of the body.
What is nondisjunction?
When homologous chromosomes fail to separate in meiosis
What is the result of nondisjunction?
Abnormal numbers of chromosomes may find their way into gametes resulting in a disorder
What is the most common form of trisomy?
Down Syndrome involving 3 copies of chromosome 21
How can prospective parents find out if they might be carrying recessive alleles for a genetic disorder?
Genetic testing can look for these abnormalities
What is DNA fingerprinting?
Analysis of sections of DNA that have little or no function but vary widely from one individual to another to allow identification through blood, sperm and even hair strands
What is the Human Genome project?
An ongoing effort to analyze the human DNA sequence
What is gene therapy?
Replacing an absent or faulty gene with a normal, working gene