Quiz 3 (Ch. 8) Flashcards
Chromosomes are classified as ______ when the centromere is very close to the center
Metacentric
Chromosomes are classified as ______ when the centromere is slightly off center
Submetacentric
Chromosomes are classified as ______ when the centromere is significantly off center but not at the end
Acrocentric
Chromosomes are classified as ______ when the centromere is at one end
Telocentric
What types of features do cytogeneticists use to make a karyotype? (3 things)
i) Size of the chromosomes
ii) Placement of the centromere
iii) Banding patterns
Why can mutations in duplications of genes be advantageous?
Because the mutations will often lead to a more specified function of the gene. This is advantageous because the specified function will be more efficient at performing that function
What is the removal of a segment of a chromosome called?
Deletion
What is the addition of a segment of chromosome called?
Duplication
What is it called when a segment of a chromosome is flipped in the opposite orientation?
Inversion
What is it called when a chromosomal segment is swapped between nonhomologous chromosomes?
Translocation
Euploidy
The number of sets of chromosomes in an organism
In what two ways can changes in chromosome number occur?
i) Changes in the number of sets of chromosomes (euploidy)
ii) Changes in the number of chromosomes within a set (ex: from 2 in a set to 4 in a set)
What dye is used in G-banding?
Giemsa
How is the banding pattern of a chromosome useful? (3 ways)
i) It distinguishes individual chromosomes from each other
ii) It detects changes in chromosome structure
iii) It reveals evolutionary relationships among the chromosomes of closely related species
Simple translocation
- A one-way transfer of genetic material
- A piece of a chromosome is attached to another chromosome
Reciprocal translocation
- A two-way transfer of genetic material
- Two different types of chromosomes exchange pieces, producing two abnormal chromosomes with translocations
How does a deletion occur?
Occurs when a chromosome breaks and a fragment of it is lost
How does a deletion affect the phenotype of an organism?
- Generally detrimental
- The larger the deletion, the more likely the phenotype of the organism will be changed
- If genes which are vital to the function of the organism are lost, it can be lethal
How do duplications occur?
- Caused by abnormal events during recombination
- Repetitive sequences can cause misalignment between homologous chromosomes
Nonallelic homologous recombination
When a crossover occurs between two misaligned chromosomes
Gene family
- Consists of two or more genes that are derived from the same ancestral gene
- Ex: The globin gene encodes all subunits that bind oxygen
- –Has 14 paralogs on 3 different chromosomes
In what two situations do inversions cause a phenotypic effect?
i) Break point effect - If the inversion break point occurs in a vital gene
ii) Position effect - A gene is repositioned in a way in which it affects its expression
Explain why an individual who is heterozygous for an inversion may be phenotypically unaffected but is more likely to have a child which is affected by this inversion
- The abnormality in offspring is due to crossing over within the inverted segment
- During meiosis I, pairs of sister chromatids synapse with each other
- –For the normal & inversion chromosome to synapse properly, an inversion loop must form
- –If a crossover occurs within the inversion loop, very abnormal chromosomes are produced (chromosomes having two or no
