Biology 1115 chapter 14
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What was the "blending" hypothesis?
it was the idea that genetic material from the two parents blends together
What was the "particulate" hypothesis?
it's the idea that parents pass on discrete heritable units (genes)
How did Mendel discover the basic principles of heredity?
by breeding garden peas in carefully planned experiments
What are characters?
distinct heritable features (ex. flower colour)
What are traits?
character variants (ex. purple or white flowers)
What is true breeding?
plants that produce offspring of the same variety when they self-pollinate
Mendel mated two contrasting, true-breeding varieties a process called?
The true-breeding parents are the _______________.
The hybrid offspring of the P generation are called the______________.
When F1 individuals self-pollinate, the __________ is produced.
What were the two laws that Mendel identified?
- 1. Law of segregation
- 2. Law of independent assortment
What is heterozygous?
an organism that has two different alleles for a gene
What is homozygous?
an organism with two identical alleles for a character
What Mendel called a "heritable factor" is what we now call a?
What are the 4 concepts that make up Mendel's model?
- 1. alternative versions of genes account for variations in inherited characters
- 2. for each character, an organism inherits two alleles, one from each parent.
- 3. if 2 alleles at a locus differ, then one (dominant allele) determines the organism's appearance and the recessive allele has no effect.
- 4. law of segregation, which states that the 2 alleles for a heritable character separate during gamete formation and end up in different gametes
Alteration versions of a genes are now called?
Each gene resides at a specific locus on a specific chromosome, what is a locus?
location or position on a chromosomes
In the true breeding plants of Mendel's P generation, the two alleles at a locus on a chromosome __________.
may be identical
Two alleles in F1 hybrids at a locus may ________.
What does the segregation of alleles correspond to in meiosis?
corresponds to the distribution of homologous chromosomes to different gametes in meiosis
P generation HAS to be?
What is phenotype?
What is genotype?
What does the law of segregation state?
states that the two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes.
What does the law of independent assortment state?
states that each pair of alleles segregate independently of each other pair of alleles during gamete formation
The law of independent assortment applies only to?
genes on different, non-homologous chromosomes
Genes located near each other on the same chromosome tend to be _____________>
When will Mendelian patterns not be the right situation to follow? (3)
- When alleles are not completely dominant or recessive
- when a gene has more than two alleles
- when a gene produces multiple phenotypes
When does complete dominance occur?
occurs when phenotypes of the heterozygote and dominant homozygote are identical
What is incomplete dominance?
the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
What happens in codominance?
two dominant alleles affect the phenotype in separate distinguishable ways
What is Tay-Sachs disease?
- a dysfunctional enzyme causes an accumulation of lipids in the brain
In Tay-Sachs disease, at the organism level, is the allele recessive or dominant?
At the biochemical level, the phenotype of Tay-Sachs disease is?
At the molecular level in Tay-Sachs disease, the alleles are?
What is pleiotropy?
genes that have multiple phenotypic effects
What is epistasis? What is an example?
- a gene at one locus alters the phenotypic expression of a gene at a second locus
- coat colour in mice and other mammals
What are quantitative characters? What does is usually indicate?
- are those that vary in the population along a continuum
- polygenic inheritance
What is polygenic inheritance? what is an example?
- an additive effect of two or more genes on a single phenotype
- ex. skin colour in humans
What is the norm of reaction? What is an example?
- is the phenotypic range of a genotype influenced by the environmenthydrangea flowers of the same genotype range from blue-violet to pink, depending on soil acidity
Polygenic characters are called multi-factorial because?
because genetic and environmental factors collectively influence phenotype
Am organism's phenotype reflects it's ____________ and_________________________.
- overall genotype
- unique environmental history
What are 3 reasons why humans are not good subjects for genetic research?
- generation time is too long
- parents produce relatively few offspring
- breeding experiments are unacceptable
What is a pedigree?
is a family tree that describes the interrelationships of parents and children across generations
Recessively inherited disorders show up only in individuals __________ for the allele.
What are carriers?
are heterozygous individuals who carry the recessive allele but are phenotypically normal
what is an example of a recessive condition?
What is consanguineous matings?
mating between two close relatives
What does the cystic fibrosis allele result in?
results in a defective or absent chloride transport channels in plasma membrane.
Dominant alleles that cause a lethal disease are _____ and arise by mutation
form of dwarfism caused by a rare dominant allele
What is Huntington's disease?
degenerative disease if the nervous system
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