Vocab:
- chracter
- - heritable feature that varies among individuals
- trait
- - variant for a character
- true-breeding
- - homozygous;parents with a particular phenotype produce offspring with the same phenotype
- hybridization
- - cross breeding
- P generation
- - true bred monozygous
- F1 generation
- - hybrid offspring of P generation
- F2 generation
- - self pollinated F1 offspring
- allele
- - alternate version of the same gene
- dominant allele
- - alle that shows on the physical appearance
- recessive allele
- - allele that doesn't show on the phenotype
- Law of Segregation
- - two alleles for each character seperate during gamete formmation
- Punnet Square
- - a chart used to list genotype possibilites and traits
- homozygous
- - same traits for one alle (TT)
- heterozygous
- - 2 different types of trait for one alle (Tt)
- phentotype
- - physical appearnce of an organism
- genotype
- - genetic make up
- testcross
- - determines if an individual showing a dominant trait is homozygous or heterozygous
- monohybrid
- - cross involving the study of one chracter ex:color
- dihybrid
- - cross involving the study of two characters ex:color and shape
- Law of Independent Assortment
- - each pair of alleles will seperate independantly during gamete formation
- complete dominance
- - one alle is dominant on the phentotype more than the other
- incomplete dominance
- - both alles are evenly dominant affecting the phenotype, where F1 hybrids have an appearance that's in bewtween that of the two parents
- codominance
- - both alles are dominant and they affcect the phenotype in different and equal ways
- Tay-Sachs Disease
- - cause by an allele that codes for a dysfunctional enzyme that can't break down certain lipids in the brain, then the lipids build up in the brain cells -and the child suffers from blindness, seizures, and degenerate brain functions, follwed by death
- multiple allele inheritance
- - there are many alleles for different phenotypes for one trait, the inheritance of the trait illustrates either incomplete dominance or codominance of --the alleles
- pleiotrophy
- - property of a gene that causes it to have multiple effects on the phenotype
- epistasis
- - a gene at one locus of a chromosome alters the effects of a gene at another locus
- quantitative chracters
- - charcters in a population that vary along in gradiations (or continuum)
- polygenic inheritance
- - 2 or more genes have an additive effect on a single chracter in the phenotype
- norm of reaction
- - range of phenotype possibilities due to environmental influences
- multifactorial chracters
- - many factors, both genetic and environmental, influence phenotypes
- pedigree
- - diagram showing family relationships across two or more generations
- carriers
- - heterozygous parents who contain a gene that is passed down
- cystic fibrosis
- - a mutation in an allele that codes for a cell membrane protein that helps transort chloride ions in and out of cells, the chloride builds and becomes --thick and sticky, leading to organ problems and recurrent bactertial infections
- sickle-cell disease
- - caused by an allele that codes a mutated hemoglobin that grows longrods when the oxygen levels in the blood are low, the rods clogg small vessels, --creating pain, organ damage, and paralysis
- Huntington's Disease
- - caused by a lethal dominant allele, nervous system detteriorates, isn't noticeable until one is aged 35-40
- amniocentisis
- - a type of test that looks for genetic disorders in a fetus or newborn, where a sample of amniotic fluid is taken then anaylsed with results weeks after --the biochemical testing
- chorionic villus sampling (CVS)
- - a type of test that looks for genetic disorders in a fetus or newborn, where a sample of the placenta tissue is taken (chorionic villus), the results can --come in hours later after the biochemical tests and the karyotyping
answers to study guide questions:
1. -true breeding- homozygous;parents with a particular phenotype produce offspring with the same phenotype
__hybridiztion- crossing of two different species
__monohybrid cross- cross involving the study of one chracter
__F1 generation- hybrid offspring of P generation
__F2 generation- self pollinated F1 offspring
__P generation- true bred monozygous
2. -Dominant means that the gene is noticeable on the phenotype while recessive is still in the genetic make up, but it doesn't affect the phenotype. __Genotype is an organism's genetic make-up while phenotype is an organism's physical charcteristics (apperance). Homozygous means that an __organism has the same traits for one allele (TT), while heterozygous means that an organism has two different traits for one allele (Tt).
5. -pleiotrophy- property of a gene that causes it to have multiple effects on the phenotype
__ex: sickle cell disease and cystic fibrosis have multiple symptons due to one deffective gene
__epistasis- a gene at one locus of a chromosome alters the effects of a gene at another locus
__ex: albinism happens because a seperate gene that makes the pigment is defective, although the individual may have genes coded for pigments
4. -With complete dominace, the phenotype is subjected to one dominant allele. With incomplete dominance, the phenotype will be a mix of both __alleles from each parent. With codominance, both alleles are dominant, but are expressed in different and equal ways
3.
__
| eggs down |
sperm across |
| ____ |
X |
x |
| X |
XX |
Xx |
| x |
Xx |
xx |
The phenotype ratios for F2 are 3 brown : 1 black because the X is dominant and for xx both are recessive and the genotype ratios are 1 homozgous :2 heterozygous : 1 recessive homozygous. The probability of a trait to be dominant (with a X) will be 3/4, if X is a gene that codes for brown petal color, then that's the probability for brown.
6. -Lethal dominant genes are rarer than lethal recessive genes because they can't be passed from genertaions, unlike lethal recessive genes. Most ----populations have the lethal recessive recessive gene for a trait more than a life-threatening lethal dominant gene that doesn't get passed down, ----because the carriers could have died before they reproduced.
7. -Carrier recognition is used identiify the carriers and their genotypes (family history), then genetic counseling can be provided to find the probability of an offspring inheriting certain traits and diseases. Fetal testing takes blood and tissue samples from a fetus to karyotype the genome, results ----varrying depending on if the test is CVS or amniocentisis, and newborn screening is another genetic counseling technique that locates factors for ----genetic disorders.
8. -To predict the probability for a specific genotype outcome, use the law of multiplecation. For example; if there are 4 possible alle combinations for ----one trait and there are 4 combinations for another another trait, then the probability for one trait would be 8/16.
