inheritance SWA
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Gene
Sequence of nucleotides on Dna that code for particular protein
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locus
site on a chromosome occupied by a gene
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dominant
a gene always expressed when present
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recessive
gene only expressed in a homozygous pair
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codominant
both alleles contribute to the phenotype
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phenotype
characteristics of an organism
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genotype
alleles in organism
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homozygous
alleles are the same (HH / hh)
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heterozygous
alleles are different (Hh)
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F1
first gen in genetic cross, starts with pair of homozygotes
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F2
Second gen produced by crossing F1 gen
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autosomes
chromosome that isn’t a sex chromosome (1-22 in humans)
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sex chromosomes
X and Y, pair 23 in humans
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whats codominance
both alleles expressed in phenotype
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whats incomplete dominance
blend of both alleles can be seen in phenotype
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what did mendel study and why
pea plants
easy to grow
short life cycle
easily observable characteristics
easy to grow
short life cycle
easily observable characteristics
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describe the easily distinguishable characteristics on pea plants
controlled by single genes
on different chromosomes
on different chromosomes
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what are monohybrid crosses
single gene inheritance
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whats is mendels first law
law of segregation
characteristics of organism are determined by factors (genes) that are in pairs
only one member of pair of factors (genes) can be represented in a gamete
characteristics of organism are determined by factors (genes) that are in pairs
only one member of pair of factors (genes) can be represented in a gamete
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what are linked genes
genes located on same chromosome, inherited together
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what are unlinked genes
genes located on different chromosomes
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what is dihybrid inheritance
2 genes inherited
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what is independent assortment
indp asst of chromosomes happens in meiosis
unlinked genes can combine to form 4 kinds of gametes
unlinked genes can combine to form 4 kinds of gametes
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what pea seeds did mendel experiment with
dominant yellow / round
recessive green / wrinkled traits
recessive green / wrinkled traits
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what ratio is expected when genes are not linked
medelian ratio- 9:3:3:1
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how can linkage be detected
if expected ratio isnt found in offspring
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what is chi squared
stats test to determine if numbers and phenotypes of offspring produced is close to mendelian ratio
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whats the null hypothesis
statement, either eg.
no difference between observed and expected results of cross
either reject or accept
no difference between observed and expected results of cross
either reject or accept
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what are degrees of freedom
number of outcomes -1
eg if 4 outcomes then degrees of freedom=3
eg if 4 outcomes then degrees of freedom=3
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whats mendels second law of segregation
the law of independent assortment
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what is sex linkage
sex linked genes are on the sex chromosomes
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how are sex linked genes written
superscript on chromosome (above it)
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what is haemophilia
disease caused by recessive allele for factor 8 that doesnt code for normal blood clotting factor
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what is dmd
progressive muscle disease caused by sex linked recessive allele that doesnt code correctly for the protein dystrophin
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what is a mutation
spontaneous random change in a gene
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when are mutation rates increased
in organisms that have short life cycles or frequent cell division
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when does mutuation occur most
during cross over in prophase 1 and non-disjunction in anaphase 1&2
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what are advantageous mutations
mutation affect protein synthesis- so change phenotype
leads to variation in species- cause evolution by natural selection
leads to variation in species- cause evolution by natural selection
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what are disadvantageous mutations
protooncogenes can mutate to become oncogenes causing uncontrolled cell division to form cancer
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whats a gene point mutation