Chapter 9 Flashcards
Pattern's of Inheritance
study of genetics can be traced back to what greek physician ?
hippocrates
“blending” hypothesis
heredity material from male and female parent blend together to get a mix of both within the offspring
why was the “blending” hypothesis rejected ?
it did not explain why some traits disappear in one gen. then reappear in later gens.
a female bird w/ a yellow beak bred w/ a male bird w/ a blue beak will lead to what color beak according to the blending hypothesis ?
offspring w/ green beaks only
heredity
transmission of traits from one gen. to the next
genetics
the scientific study of heredity
- modern work began by gregor mendel in 19th century (1800s)
main point of mendel’s research ?
heritable factors (genes) retain their individuality from gen. to gen.
- no blending
character
heritable feature that varies among a population
- eye color, hair color, etc.
trait
variant of a character within a population
- black hair / eyes, blonde hair, blue eyes, etc.
carpel of a pea flower
contains eggs
stamens of a pea flower
releases sperm-containing pollen
true-breeding
sexual reproduction where offspring produced are identical to parent
- organisms are homozygous
hybrids
offspring that differ in one or more inherited traits from parents of different species / same species parents but from two different true-breeding pools
- heterozygous for one or more genes
cross
mating of two sexually reproducing organisms
- controlled mating
the three generations in inheritance (P, F1, F2)
- parental gen. (grandparents; true-breeding)
- first filial gen. (parents; hybrid gen.)
- second filial gen. (grandchildren)
what is always the outcome between two different true-breeding organisms ?
offspring will always be hybrids
- will always display the dominant allele
F2 gen. phenotype ratio of monohybrid cross?
3 : 1 (dominant : recessive)
F2 gen. genotype ratio of monohybrid cross?
1 : 2 : 1 (XX : Xx : xx)
F1 gen. must contain what two factors ?
both dominant and recessive alleles
first law of inheritance
there are alt. versions of genes that account for inherited characters
second law of inheritance
for each character, organism inherits two, one from each parent
third law of inheritance
if two alleles differ, then one determines the appearance and the other is masked
- dominant masks recessive
fourth law of inheritance
sperm / eggs carry only one allele for each inherited characteristics
allele
alt version of a gene
homozygous
having two identical alleles for a gene
heterozygous
having two different alleles are a gene
dominant allele
allele that determines organisms phenotype when heterozygous
recessive allele
no noticeable effect on organism when heterozygous
law of segregation
two alleles separate during meiosis (I)
- each gamete results in only one allele for each gene
punnet square
diagram used to show random fertilization inheritance
genotype
genetic makeup of organism
phenotype
expressed traits of organism
what law of inheritance explains why traits that disappear in F1 gen. reappear in F2 gen. ?
law of segregation
- fusion of gametes creates allele pairs once again
how can two plants w/ different genotype have same phenotype ?
one could be homozygous dominant and the other heterozygous
locus
site where gene is found on chromosome
- homologs have same loci sites
what step of meiosis is the segregation of alleles occurring ?
during meiosis I, when homologs separate
monohybrid cross
mating between HETEROZYGOUS organisms for ONE character
dihybrid cross
mating between HETEROZYGOUS organisms for more than two characters
law of independent assortment
pair of alleles segregate independently of other pairs
- inheritance of one character does not affect inheritance of another
F2 gen. phenotype ratio of dihybrid cross ?
9 : 3 : 3 : 1 (normal/normal, normal/affected, affected/normal, affected affected)
testcross
mating between unknown dom. organism (XX / Xx) and recessive organism
rule of multiplication
probability of multiple independent events happening at once
rule of addition
the probability of the same event occurring in two or more alt. ways
pedigree
family genetic tree showcasing heritable traits across gens.
mutant trait
trait less common in nature
wild type
trait most common in nature
carriers
organism who is heterozygous for recessively inherited disorder
- do not show symptoms
complete dominance
type of inheritance where phenotypes of heterozygote and homozygous dom. are identical
incomplete dominance
type of inheritance where phenotypes of heterozygote is completely new / different from homozygous dom. / recessive parent
F2 phenotypic ratio of organism w/ a characteristic that displays incomplete dominance
1 : 2 : 1 (dom. : hetero. : recessive)
why doesn’t a cross between organisms that display incomplete dominance for a characteristic support the blending hypothesis ?
because not all of the offspring will be a blend between both parents, some will inherit the same exact phenotype as one of the parents
ABO blood group
blood phenotypes in humans arising for 3 alleles of a single gene
why is it important for blood donors to be the same blood type as blood recipients ?
introducing a different blood type w/ a foreign carbohydrate will cause the recipients immune system to produce antibodies; making the blood clump which can lead to death
codominance
inheritance pattern where in heterozygotes express traits of both dom. / recessive alleles
pleiotropy
single gene controls more than one phenotypic trait
polygenic inheritance
two or more genes influence one characteristic
difference between pleiotropy and polygenic inheritance
OPPOSITES;
pleiotropy = one gene influences multiple characters
polygenic = multiple genes influence one character
what are the two main things that influence characters ?
heredity / environment
- combination of both affect all characters
If most characters result from combo of environment / heredity, why was mendel able to ignore environmental influences in his pea plants ?
all characteristics were determines by heredity AND he maintained a controlled and same environment for all of them
how does heredity / environmental factors affect ABO blood group ?
heredity = very specific phenotype w/ NO environmental influence
environmental = how much RBC is in the blood (overall health / lifestyle)
chromosome theory of inheritance
- genes are located on chromosomes
- behavior of chromosomes during meiosis / fertilization influence inheritance patterns
which law has their physical basis in the following phases of meiosis:
1) the orientation of homologous chromosome pairs in metaphase I
2) the separation of homologous chromosomes in anaphase I?
1) law of independent assortment
2) law of segregation
sex chromosomes
chromosomes that determine sex; X / Y
sex-linked genes
gene located on a sex chromosome (X / Y)
where are majority of sex-linked genes on ?
X chromosome
- Y is much smaller and less significant
X-linked gene
gene located on X chromosome
inheritance pattern of X-linked genes
majority of sex-linked genes are X-linked
- males have 1 copy
- females have 2
how are females affected by X-linked genes ?
only if both X chromosomes are affected by the gene
- if only one chromosome is affected = carrier
how are males affected by X-linked genes ?
if their only X chromosome is affected
autosomal dominant traits are passed down how ?
dom. allele from at least one parent
autosomal recessive traits are passed down how ?
recessive allele from BOTH parents
