bio 23
What is Huntington's disease?
progressive degeneration of brain cells, neurological
after the genotype and phenotypes of offspring are determined, we can determine the
ratios
for a recessive trait to result the individual must have 2 copies of the recessive allele
recessive
lowercase letter is
recessive allele
9:3:4
recessive epistasis. homozygous recessive allele masks both alleles of another gene.
9:3:3:1
regular dihybrid cross
the chance of 2 or, more independent events occurring together is the product of their chance of occurring separately is?
the product rule of probability
What is a pedigree?
Chart of genetic relationship of family individuals across generations.
results in polygenic inheritance is what
the result is a continuous range of phenotypes
homozygous dominant individual and heterozygous individual will have
the same phenotype in this instance
what represents the recessive allele
the small letter represent the recessive allele
what if the parents were each Ff ( monohybrid)
then sperm could have either F or f, and eggs also could have F or f
autosomes do not include what
those chromosomes that determine gender ( X and Y)
example of incomplete dominance
true-breeding red flowers is crossed with a true-breeding white flower yields all pink flowers. Because cross of two pink flowers yields an offspring phenotypic ratio of 1 red: 2 pink: 1 white. Sickle-cell disease is an another example
what is homozygous dominant
two dominant alleles (BB)
autosomal recessive disorder requires presence of
two recessive alleles
example of Codominance
type AB blood has both A antigens and B antigens on red blood cells
what is a genotype
genetic makeup of an individual
a genetic makeup of an individual
genotype
what is phenylketonuria
metabolic disorder that affects nervous system development
what are some symptoms of Ta-sachs disease
neurological impairment , psychomotor difficulties, blindness, uncontrollable seizures, eventually paralysis
can there be two letter in a gamete that are same
no two letter in a gamete can be the same letter of the alphabet
autosomal dominant disorder only requires the presence of
one dominant allele
homologous chromosomes have one of each pair is ____, the other is _____
paternal and maternal
when do the first signs of Huntington disease usually appear
patients appear normal until middle aged, but in some cases, the first signs appear during teen years
physical appearance of the individual (tall or short, red or white)
phenotype
9:3:3:1
phenotypic ratio of a dihybrid cross
what is a phenotype
physicals appearance of the individual (tall or short, red or white)
using the product rule
probability of something X probability of something = answer
what are some symptoms and causes of having cystic fibrosis
-Thick, abnormal mucus production -lungs, bronchial tubes, pancreatic ducts affected -interferes with respiration and digestion
2 copies of the recessive allele (bb)
2 copies of the recessive allele (bb)
what is homozygous recessive genotype
2 copies of the recessive allele (bb)
Autosomes
22 pairs of chromosomes that do not determine sex
what is the cause of phenylketonuria
A defect in the step that converts phenylalanine into tyrosine and a lack of enzyme for phenylalanine metabolism
What is a heterozygous genotype?
A genotype which contain both a dominant and recessive allele (Bb)
explain the purpose of a testcross
A testcross is conducted to determine if an individual that is expressing a dominant allele is heterozygous or homozygous for that gene
what president was thought to have Marfan syndrome
Abraham Lincoln
what is recessive allele
Allele that exerts its phenotypic effect only in the homozygote; its expression is masked by a dominant allele.
What is a allele?
Alternative form of a gene; alleles occur at the same locus on homologous chromosomes.
Who was Gregor Mendel?
Austrian monk who developed some of basic laws of heredity in the 1860s. was also first to state that plants have two factors for every trait that are transmitted from parents to offspring
What is Marfan syndrome?
Autosomal dominant genetic disorder of the connective tissue, specifically the fibrillin protein.
what is Huntington disease
Autosomal dominant genetic disorder that affects the nervous system; results in a progressive loss of neurons in the brain.
distinguish between autosomal recessive and autosomal dominants genetic disorders
Autosomal recessive disorders result from the inheritance of two recessive alleles. The child is affected and is homozygous recessive, but neither parent is because they are heterozygous. In autosomal dominant disorders, both parents are affected but the child can be unaffected
what is phenylketonuria (PKU)
Autosomal recessive genetic disorder that causes a lack of the enzyme that metabolizes phenylalanine; the accumulation of phenylalanine causes problems with nervous system development and function.
What is sickle cell disease?
Autosomal recessive genetic disorder that causes a malformation of hemoglobin molecules, causing red blood cells to form a sickle shape; also sometimes called sickle-cell anemia due to the symptoms of the disease.
what is Tay-Sachs disease
Autosomal recessive genetic disorder that results in a deficiency in the enzyme hexosaminidase A; causes an accumulation of glycolipids in the lysosomes, resulting in a progressive loss of psychomotor functions.
In the cross Ff x Ff, what is the chance of obtaining either a F or a f from a parent?
Chance of F= 1/2 and the chance of f=1/2
what represents the dominant allele
Capitol letter represent the dominant allele
what occurs when both alleles are equally expressed
Codominance
9:7
Complementary. one dominant allele of each 2 genes is necessary to produce the phenotype
what is monohybrid cross
Cross between parents that differ in only one trait. (Ff x Ff)
What is a dihybrid cross?
Cross between parents that differ in two traits.
what is testcross
Cross, between an individual with a dominant phenotype and an individual with a recessive phenotype, to determine whether the dominant individual is homozygous or heterozygous.
Capital letter is
Dominant allele
12:3:1
Dominant epistasis I: dominant allele of one gene hides the effects of both alleles of another gene
13:3
Dominant epistasis II: Dominant allele of one gene hides effects of dominant allele of another gene
if the genotype is FfSs (looking at 2 traits), gametes can contain any of
FA, Fs , fS, or fs
what is genotype
Genes of an organism for a particular trait or traits; often designated by letters—for example, BB or Aa.
what is cystic fibrosis (CF)
Genetic disease caused by a defect in the CFTR gene, which is responsible for the formation of a transmembrane chloride ion transporter; causes the mucus of the body to be viscous.
What is familial hypercholesterolemia?
Genetic disorder that causes an accumulation of cholesterol in the blood due to defects in the LDL receptors on the cell surface.
Phenotype A
Genotype IAIA or IAi
Phenotype AB
Genotype: IAIB
Phenotype B
Genotype: IBIB or IBi
Phenotype O
Genotype: ii
member of a pair of chromosomes that are alike and come together during synapsis
Homologous chromosomes
gene for defective proteins are called
Huntington
progressive degeneration of brain cells, neurological is what autosomal dominant disorders
Huntington disease
ABO blood types
I^A = A antigens on RBCs I^B = B antigens on RBCs i = has neither A nor B antigens on RBCs
Discuss how studies using identical twins may help determine how much of a phenotype is based on genetics and how much is environmental.
Identical twins have identical genomes and have developed from identical oocytes containing the same cytoplasmic composition. However, the expression of their genes is influenced by environmental inputs. Variation between identical twins is attributed to the inputs from the environment on their development
what is locus
Physical location of a trait (or gene) on a chromosome.
controlled by 2 or more sets of alleles is what
Polygenic inheritance
if there are _______ _______ produce with the _________ phenotype, then the _______ ______ ____ __ ___________
If the are ANY OFFSPRING produced with the RECESSIVE phenotype, then the UNKOWN PARENT MUST BE HETEROZYGOUS
What is incomplete dominance?
Inheritance pattern in which an offspring has an intermediate phenotype, as when a red-flowered plant and a white-flowered plant produce pink-flowered offspring.
what is codominance
Inheritance pattern in which both alleles of a gene are equally expressed in a heterozygote.
what is multiple alleles
Inheritance pattern in which there are more than two alleles for a particular trait; each individual has only two of all possible alleles.
caused by defect in an elastic connective tissue protein called fibrillin is what kind of autosomal dominant disorder
Marfan syndrome
Name some autosomal dominant disorders
Marfan syndrome, Huntington disease
each pair of factors separates independently all possible combinations of factors can occur in the gametes
Mendel's law of independent assortment
each individual has two genes for each trait, the factors segregate during the formation of gametes. each gamete contains only one gene from each pair of genes. Fertilization gives each new individual 2 genes for each trait, one from each parent
Mendel's law of segregation
what is law of segregation
Mendelian principle that explains how, in a diploid organism, alleles separate during the formation of the gametes.
each pair of factors separates independently so that all possible combinations of factors can occur in the gametes is what
Mendell's law of independent assortment
the gene exists in several allelic forms, but each person still has only 2 of the possible alleles
Multiple allele inheritance
what is homozygous
Possessing two identical alleles for a particular trait.
what is heterozygous
Possessing unlike alleles for a particular trait.
ABO blood groups often used
Paternity Testing
what can disprove paternity but not prove it
Paternity testing
what is polygenic inheritance
Pattern of inheritance in which a trait is controlled by several allelic pairs.
metabolic disorder that affects nervous system development is what?
Phenylketonuria
one way to figure out the possible combinations of eggs and sperm that could occur is to use a
Punnett square
15:1
Redundancy: one dominant allele of either of two genes is necessary to produce phenotype
Another antigen on RBCs
Rh factor
the chance of an event that can occur in more than one way is the sum of the individual chances
Sum rule of probability
Name some autosomal recessive disorders.
Tay-Sachs disease, cystic fibrosis, Phenylketonuria (PKU), Sickle-cell disease,
What is a dominant allele?
The allele that exerts its phenotypic effect in the heterozygote; it masks the expression of the recessive allele.
summarize Mendel's laws of segregation and law of independent assortment
The law of segregation states that each individual has two factors for each trait and these factors separate during gamete formation such that each gamete contains only one factor. At fertilization, the zygote receives two factors for each trait. The law of independent assortment states that during gamete formation, each pair of factors separates independently of other factors and that all possible combinations of factors can occur
What is the law of independent assortment?
The mendelian principle explains how combinations of traits appear in gametes; see also independent assortment.
Determine the genotype of the child, the mother, and the possible genotype of the father for a child with type O blood who is born to a mother with type A blood.
The mother has to be heterozygous for type A blood, and the second allele for type O blood would have come from the father. He could have been heterozygous for type A, type B, or type O blood.
what is phenotype
Visible expression of a genotype—e.g., brown eyes or attached earlobes.
what is Punnett square
Visual representation developed by Reginald Punnett that is used to calculate the expected results of simple genetic crosses.
interpret the genotype of the heterozygote if the inheritance pattern for a genetic disorder is shown to be incompletely dominant
With incomplete dominance, the heterozygote exhibits a phenotype that is intermediate between the homozygous recessive and the homozygous dominant
if genotype is Ff, the gametes from this individual will contain either
a F or f
3:1 phenotypic ratio is always expected to be what
a monohybrid cross
Describe the types of crosses that results in a 3:1 and a 9:3:3:1 ratio
a phenotypic ratio of 3:1 results from a one-trait cross and a ratio of 9:3:3:1 results from a two-trait cross
in polygenic inheritance each dominant allele codes for a product and effects are
additive
if the dominant individual is homozygous for both traits,
all offspring will show the dominant phenotypes
letters indicate
alleles
Rh positive people have the
antigen
presence of what is dominant
antigen
when does the symptoms begin to appear for Tay-sachs disease
between ages 4-8 months
1:2:1
cross between hybrids (AaxAa) when there is incomplete or codominence
2:1
cross between hybrids when one allele is recessive lethal that has a dominant effect on a visible phenotype
what is the most common lethal genetic disorder in Caucasians in U.S
cystic fibrosis
when does death happen with Huntington disease
death usually 10-15 years after symptom onset
when does someone usually die with Tay-sachs disease
death usually by 3-4 years of age
homozygous recessive individual will have a
different phenotype
a certain trait will result if the individual has at least 1 dominant allele
dominant
Mendel's Law of Segregation
each individual has two genes for each trait, the factors segregate during the formation of gametes. each gamete contains only one gene from each pair of gene. Fertilization gives each new individual 2 genes for each trait, one from each parent
Mendell's Law of Independent Assortment
each pair of factors separates independently so that all possible combinations of factors can occur in the gametes
summarize the environmental factors that may influence polygenic traits such as height and skin color
environmental factors include nutritional status, diet, temperature, and exposure to sunlight
name a incompletely dominant disorder
familial hypercholesterolemia
1 copy of the dominant allele and 1 of the recessive (Bb)
heterozygous
what types of chromosomes have the same genes at the same loci
homologous chromosomes
true breeding means
homozygous
2 copies of the dominant allele (BB)
homozygous dominant
what are the different types of genotype
homozygous dominant, heterozygous, homozygous recessive
what is are some example of polygenic inheritance?
human height and skin pigmentation
Heterozygous individual has a phenotype intermediate to the two homozygous individuals
incomplete dominance
1:2:1 ratio
incomplete dominance and codominance
no two letters in a gamete can be the same
letter of the alphabet
skin color is controlled by
many gene (over 100) and many alleles
homologous chromosomes contain the
same genes at the same loci
during meiosis, homologous chromosome do what
separate so there is only 1 member of each pair in a gamete
internal hemorrhaging leads to complications such as jaundice, episodic pain in the abdomen and joins, and damage to internal organs. Also, poor circulation, anemia, and low resistance to infections are symptoms of what autosomal disease
sickle cell
red blood cells are irregulars in shape, often sickle shaped is what type of autosomal recessive disorder
sickle-cell disease
what are some symptoms of Marfan syndrome
symptoms include the dislocated lens of the eye, long limbs and fingers, and a caved-in chest
what are some examples of environmental influences
temperature, nutrition
branders of plants and animals may do a _________ to determine the likely genotype of an individual with the dominant phenotype
testcross
Rh negative people lack
the Rh factor
what can influence gene expression and therefore phenotype
the environment
distinguish between the terms genotype and phenotype
the phenotype of an individual is tis appearance, which is determined by the genes it carries for traits carried in its genome. The genes present in the genome comprise its genotype.
