Real Bio Exam 4 Study Guide

michelleburkee2's version from 2015-11-15 05:45

Section 1

Question Answer
the process by which the traits of organisms are passed to their offspringinheritance
encode characteristicsgenes
genes are the unit of heredity
the location of a gene on its chromosome is called itslocus (loci)
how many pairs of chromosomes do humans have?23
a pair of chromosomeshomologous chromosomes
where are genes for the same characteristic found?at the same loci (locus) on both homologous chromosomes
alternative versions of genes found at the same gene locus are calledalleles
if both chromosomes have the SAME alleleshomozygous
if chromosomes have different allelesheterozygous
what are the source of alleles?mutations
mutations definitionchanges in the nucleotide sequence in genes
How can a mutation be passed onif it occurs in gametes
most mutations initially appear in thegametes
another word for homozygous istrue breeding
A cross between a purple flower plant PP and a white flowered plant pp produces what genotype(s)? And what phenotype(s)?Pp is genotype and purple flower phenotype
What genotype(s) and phenotype(s) are produced when a heterozygous purple Pp and a heterozygous purple Pp breed?1/4 PP, 1/4 pp, and 1/2 Pp for genotype. 3/4 purple and 1/4 white for phenotype.
how many alleles are there for a given gene characterstic (except for gametes)?two
gametes carry how many alleles per characteristic?one

Section 2

Question Answer
A piece of DNA that encodes info needed to produce proteins, cells, an entire organismsgene
what are homologous chromosomes?a pair of chromosomes that carry genes for the same characteristics
what are alleles?alternative versions of a gene that are found at the same locus.
what happens to the alleles during meosis?the two alleles for a trait seperate during meosis to form gametes.
Gametes produced by a homozygous parent during meosis AA(AA)--> (A) (A)
gametes produced by a heterozygous parent during meosis Aa(Aa)--> (A) (a)
when do homologous chromosome pairs seperate?in Anaphase I of meosis
Each gamete receives _______ one of each pair of homologous chromosomes and thus one of the two alleles per trait
Mendel's Law of Segregation statesthe two alleles on homologous chromosomes seperate from each other during meiosis
each trait is determined bypairs of genes
each organism has how many alleles for each gene?two. One on each homologous chromosome
how do chromosomes seperate during meiosis?at random. the distribution of alleles to the gametes are also at random.
a ___ is used to deduce whether an organism with a dominant phenotype is homozygous for the dominant allele or heterozygoustest cross
the law of independent assortment statesthe indepedent inheritance of two or more traits
Gametes of SsYySY, sY, Sy, and sy
what is the physical basis for independent assortment of alleles?random segregation of homologous chromosomes during metaphase 1 .
The independent assortment of alleles only works when? why?when the traits are on DIFFERENT chromosomes because they are unlinked (they segregate independently). If they were on the same chromosome it does not work like this.
The Mendelian rules of inheritance state1.) each trait is completely controlled by a single gene 2.)only two possible alleles of each gene exist 3.) one allele is completely dominant to the other, recessive allele.
Exceptions to mendelian inheritance include (5)1.)incomplete dominance 2.)multiple alleles 3.)co-dominance 4.)polygenic 5.)pleitrophy
incomplete dominance (or blending) def. and an examplethe phenotype of a heterozygote is a mix of dominant and recessive allele. ex. hair texture
multiple alleles def. and 2 examplestraits that are determined by more than 2 alleles. ex. blood type and hair color
co-dominance def. and an exampleboth alleles contribute to phenotype and do not mix. i.e. blood type
polygenic def. and an 2 examplesone trait determined by multiple genes i.e. eye color and skin color
pleitrophy def. and exampleone gene has multiple effects i.e. sickle cell anemia

Section 3

Question Answer
Incomplete dominance hair texture example: HH(straight)*WW(curly hair)=?HW (wavy hair)
multiple alleles:an individual may have at most two different gene alleles for a gene, but a SPECIES may have multiple alleles for a given characteristic
blood type multiple alleles example. Alleles: 1.)A+A=? 2.)A+O= ?3.)A+B=?. What genotype and what phenotype(blood type)?genotype: AA, OA, and AB. phenotype: A, A, and AB
blood type codominance (blood type):alleles A and B are dominant to O. In AB individuals the plasma membrane cells have both A and B. The heterozygotes express the phenotype of both of the homozygotes (A and B).
sickle cell anemia is an exmaple of____. why?pleitropy. it can have more than one effect: 1. sickling of cells 2. protection from malaria
the ______ of an organism affects its phenotypeenvironment
gene linkagegenes on the same chromosome tend to be inherited together
ex. of gene linkagethe genes for flower color and pollen are linked
crossing overcreates new combinations of linked alleles
another term for crossing overgenetic recombination

Section 4

Question Answer
when can genetic recombination occur?during Meosis I
where are sex linked genes only found?on the x or y chromosome
what are sex linked genes?genes carried on one sex chromosome but not on the other
the _ chromosome is bigger than the _ chromosomethe x chromosome is bigger than the y chromosome
autosomal dominant affected individual in every generation
recessive traitoften skips a generation
nondisjunctionthe incorrect seperation of chromosomes or chromatids in meiosis
what does nondisjunction cause?gametes to have too many and too few chromosomes
down syndromeabnromal numbers of autosomes on 21st pair there is an extra chromosome. 47 chromosomes in total.

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