Chapter 14&15 Flashcards
Compete Dominance
phenotypes of heteroztgote and dominant homozygote are indistinguishable
Incomplete dominance
phenotyoes of heterozygotes is intermediate between the two phenotypes of both homozygotes
Codominance
two alleles each affecct the phenotype in seperate distinguishable ways
Wild type
phenotype most commonly observed in the natural population
Sex-Linked gene
a gene located on sex chromosomes; usually occurs on the X chromosome; fathers transmit this and other x-linked alleles to all daughters but to no sons. Any male who inherits such allele from mother will express the triat.
Genetic recombination
production of offspring with comination of traits that differ from those found in either parent
Crossing over
reciprocal exchange of genetic material between nonsister chromatids during prophase 1 of meiosis
Nondisjunction
an errot in meiosis or mitosis in which members of a pair of homologous chromomsomes or a pair of sister chromatids fail to separate from each other
Cystic Fibrosis
- most common lethal genetic disease in US
- normal allele coded for chloride transport channels
- recessive
- cause mucus buildup in organs
- most die before 5th birthday and half to 20’s or 30’s
Sickle-Cell disease
- most common inherited disorder to African Americans
- caused by substitution of a single amino acid in hemogloblin
- Homozygous-can cause clumping and clotting
- blood transfusions can prevent other problems
- disease: both alleles are sickle cell
- -trait: one allele normal and one sickle cell
Huntington’s Disease
- degenerative disease of the nervous system
- irreversible and inevitably fatal
- lethal dominate allele; no obvious phenotypic effect until 35-40
- child born to parent with disease has 50% chance of inheriting the allele and disorder
- can have genetic testing
Muscual Dystropthy
- affect 1/3500 males born in US
- progressive weakening of the muscles and loss of corddination
- rarely live past 20
- X-linked disorder
Hemophilia
- X linked recessive disorder
- absence of one or more proteins required for blood clotting
- i.v. injections of the protein
Down’s Syndrome
- Extra chromosome 21; each body cell has 47 total
- Trisomy 21
- facial features, short, developmental delays
- increased chance of developing many diseases
- have a short life span
- frequently increase with age of mother
- most cases result from nondisjunction during meiosis 1
Klinefelter syndrome
- XXY
- Males- testes small and sterile
- Some breast enlargement and other female body characteristics are common
- May have subnornal intelligence
XYY
- Males undergo normal sexual development
- tend to be taller than average
Trisomy X (XXX)
- Famales-Healthy-Fertile
- slightly taller than average
- at risk for learning disabilities
Turner Syndrome
- Monosomy X (XO)
- Only viable monosomy in humans
- female-sterile bc sex organs do not mature
- normal intelligence
“cri du chat” -cry of the cat
- specific deletion in chromosome 5
- severally intellectualy disabled
- small head with unsual facial features
- cry sounds like a cat in distressed cat
- usually die in infancy or early childhood
CML- chronic myelogenous leukemia
- occurs when recriprocal translocation happens during mitosis of cells that will become WBC
- Exchange of a large portion of chromosome 22 with small fragment from a tip of chromosome 9 produces a much shorted chromosome 22
- causes cancer by activating a gene that leads to uncontrolled cell cycle progression
2 alleles each affect the phenotype in seperate distinguishable ways
codominance
When 2 alleles for one gene are identical the individual is said to be
homozygous
If you cross a homozygous tall pea w/homozygous dward pea, what is the phenotype of the offspring?
100% tall
A cross dealing with one trait is called
Monohybrid cross
Different gametes can result from AaBbCc
8
in a flower both yellow and tall are dominate what is the genotype
TTYY or TtYy
Crossing two pink flowers what is the phenotype
1 red
2 pink
1 white
Universal blood donor
O
Universal blood recipient
AB
Traits that are alternatives to the wild type are called
Mutant phenotypes–due to alleles assumed to have originated as changes or mutations in the wild type allele
Chromosonal basis of sex
SRY (sex-determining region Y) gene on the Y chromosome for male
A gene located on either sex chromosome is called
sex-linked gene
mothers can pass sex-linked alleles to
daughters and sons
If the sex-linked trait is due to a recessive allele, a female will express the phenotype only if she is
homozygous
If the sex-linked triat is due to a recessive allele, a male will express the trait if he recieved the recessive allele from his mother because he is
hemizygous
Have far more sex-linked recesssive disorders
Males
Sex-linked recessive disorders
- Color Blindness
- Muscular Dystrophy
- Hemophilia
Inactive X in each cell of a female condenses into a compact object called
Barr Body
Females are a mosaic of two types of cells
- those with the active X derived from the father
- those with the active X derived from the mother
Genes on the same chromosome that tend to inherit together in genetic crosses are said to be
Linked genes
Offspring that inherit a phenotype that is different from either parent are said to be
Genetic recombination
Nonparental phenotypes
accounts for the recombination of linked genes. In this end portions of two nonsister chromatids trade places each time a crossover occurs.
An ordered list of genetic loci along a particular chromosome
Genetic map
Genetic map based on recombination frequencies
Linkage map
Mishap in which the members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to seperate during meiosis 2.
Nondisjunction
Aneuploidy
If aberrant gamete unites with a normal one at fertilization the zygote will have abnormal number of a chromosome
Chromosomal fragment is lost
Deletion
When an extra segment is attatcched to a sister chromatid
Duplication
Reverses a segment within the chromosome
Inversion
Moves a segment from one chromosome to a nonhomologous pair
Translocation
Alterations of chromosome structure due to chromosome breakage
Deletion, Duplication, Inversion, and Translocation
Genes located in organelles in the cytoplasm-contain small circular DNA molecules
Mitochondria, Chloroplast, Plant Plastids
Why is almost all the mitochindrial DNA maternal?
Because almost all the mitochondria passed on to a zygote comes from the cytpplasm of the egg– instead of sperm
Reason linked genes are inherited together
located on the same chromosome
Mechanism for production of genetic recombinates
Crossing over and independent assortment
Males are more often affected by sex-linked traits than femals because
males are hemizygous for X-chromosome
What do all humans inherit from their mother?
X-chromosome and mitochrodrial DNA
Sickle celled anemia is not a??
Sex-linked disorder
A common genetic disease that causes mucus to build up in organs of the body. Is a recessive trait
Cystic Fibrosis
Lethal dominate alelle–a child has a 50% chance of inheriting this from parent who has the disease
Huntington’s disease
Trisomy 21
Down’s syndrom
Klinefelters Syndrom
XXY
Monosomy
Turner’s Syndrom
