Chromosomes, Pedigrees and Mutations 3.5 U3 Flashcards
What is gene linkage?
Genes on the same chromosomes can “break” the law of independent assortment The closer together they are, the most likely they are to be “linked”Unlikely to be split apart during crossing over in Meiosis I
What is the law of independent assortment?
Alleles get independently assorted
How are gene map units created and used?
Crossover frequencies can be converted into map units.We can use the frequency of crossing-over to determine the relative distance between genes on the same chromosome.
What is the purpose of Human Pedigrees?
Shows presence or absence of a trait according to relationships within a family across generations
Autosomal Inheritance Dominant Traits? EX
every individual with the trait must have a parent with itwithout any other context, shading = AA or AaExample = Huntington’s disease
Autosomal Inheritance Recessive Traits? EX
individual with the trait may or may not have a parent with itwithout any other context, shading = aaNon-shaded could be AA or Aa!Example = Sickle Cell Anemia
X-Linked Recessive Traits? EX
males are more likely to show recessive traitsshading = XaXa, XaYNon-shaded could be XAXA, XAXa, or XAYExample = Red-green colorblindness
What is a mutation?
A change in the genetic material
What are two main types of mutation?
Gene mutation Chromosomal mutation
What is Locus?
Location of gene or DNA sequence
What is Germ-line mutation?
From gametes
What is Somatic Mutations?
Not gametes
What is wild type protein?
normal protein
What is point mutation?
a change in one base pair of the sequence
What are the types of point mutations?
Silent, Missense, Nonsense
What is Silent Mutations?
Has no effect on the protein sequence
What is Missense Mutations?
Results in an amino acid substitution
What is Nonsense Mutations?
substitutes a stop codon for an amino acid
What is Frameshift Mutations?
A deletion or insertion of bases can cause a frameshift
What can Cause Mutations?
Spontaneous Mutationserrors in DNA replication, etc.Induced Mutationscaused by mutagens
What are some examples of disorders caused by mutations?
Sickle Cell Disease, Huntington’s Disease
What is Sickle Cell Disease?
Single gene mutation (point - substitution)Hemoglobin-Beta gene on chromosome 11Autosomal recessive“Heterozygous advantage”
What is Huntington’s Disease?
Insertion of “CAG” repeats in gene for a protein in brain neuronsChromosome 4Autosomal dominant
What is a human karyotype?
A human karyotype shows 22 pairs of autosomes and 1 pair of sex chromosomes.
When does non-disjunction happen and also what is it?
Could happen in M1 or M2If in M1 then no normal cellsIf in M2 then half normal cellsIs improper splitting of chromosomes
What is Monosomy?
1 copy
What is Trisomy?
3 copies
What is Aneuploidy?
An abnormal number of chromosomes
What is Polyploidy?
Having more than two complete sets of chromosomes Relatively common in plants, but rare in animals!
What is X-Chromosome Inactivation
In females, one X chromosomes is “switched off” and forms a Barr Body
What are lethal traits?
A trait in which a homozygous dominant individual does not survive.This affects probability estimates!
When is crossing over common?
When far apart
When is crossing over rare?
When close together(linked)
X-Linked Dominant Traits? EX
females are more likely to show dominant traits
shading = XAXA, XAXa, XAY
Example = X-linked hypophosphatemia (XLH)
