Please enable JavaScript.
Coggle requires JavaScript to display documents.
mendelar genetics ((Dominant vs. Recessive (Dominent:
alleles produce…
mendelar genetics
Dominant vs. Recessive
Dominent:
- alleles produce traits that are always expressd in the phenotype if there are present in the genotype
- represented by an upper case/ capital letter
Recessive:
- both alleles must code recessive in the genotype for it to be expressed in the phenotype
- represented by a lower case letter
genotype vs. phenotype:
phenotype = physical appearence of an individuals characteristics, (the expressed allele from the genotype)
genotype = refers to the complete combination of alleles held by an individual (weather expressed or not)
genotype options:
- homozygous dominet,
- homozygous ressesive,
- heterozygous
-
punnet squares
test crosses:
you can use a test cross to find out the genotype, when you don't know if the organism is homozygous or heterozygous
- to find the genotype of an organism, cross it with a homozygous ressesive organism
- test predictions using test crosses
- after breeding many, many times ifsom of the pffspring have ressesive phenotypes then you know the organism you were testing is heterozygous, if there are no ressesive phenotypes offspring then the test is homozygous dominent, and it can be used for pure breeding
punnet squares / monohybrid cross:
punnet squares are used in genetics to calculate the frequency/chance of the different genotyes & phenotypes among the offspring of the cross
- based on the gametes of parents
e.g.
T= black hair
t= blond hair
genotype ratio; 1TT : 2Tt : 1 tt
phenotype ratio; 3 black hair : 1 blond hair
Ratios:
(A ration is a pair of numbers that make a comparison)In genetics they tell us the
likely-hood of certain
genotypes & phenotypes, (form a breed)
- all rations form punnet squares
must be out of 4, & will be either:
4:0 or 0:4
3:1 or 1:3
2:2 or 2:2
pedigrees:
A pedigree chart is like a family tree
they give the phenotype (observed/actual) trait)symboles:
circle = represents females
square = represents males
joined togeahter = means they are a breeding pair
(coloured in = usualy means they have a ressesive phenotpe)tips:
- to find ressesive raits, look for were offspring differ from both parents
(you must be homozygous ressesive to express a ressesive traight in your phenotype. this means you must have reseves a ressesive allel form both your parents, so they mut bothe carry a ressesive allele, and if they have a dominent phenotype then they must also carry a dominent allele)
- ressesive traits often skip generations
- ressesive genes arn't always less commen than dominent ones ( but often are)
Sex determination:
sex chromosomes:
females carry (xx)
males carry (xy)
(the x chromosome is bigger than than the
y chromosome in humans)
- humans have 46 chromosomes in there body cells, 44 of these are autosomes & 2 are our sex- chromosomes (chromosome numbers 45 &46)
- when gametes are produced by meiosis each gamete carries 1 sex chromosome.
all female gametes (eggs) carry an x chromosome
1/2 male gametes (sperm) carry y and 1/2 carry x chromosomes
so the male gamete 'decides' the genderexplanation: there is a 50% chance
of having a boy or a girl
(fertilization is a random event, so previous attmepts have no effect on future outcomees. hence despite there being a 50% chance for both genders you could have 8 offspring and all of them could be boys, and then next time there is still a 50% chance of being a boy or girl)
Mendelian genetics
Mendelian genetics is the study of classic genetics. it is the idea that genetic characteristics and features are passed on through individuals and altered through evolution.
- Mendelian genetics are known as classic genetics
- discovered by Gregor Mendel
- study of how certain features are transmitted from one individual to the next
- (selective breeding was discovered by Mendel, and is still used today to produce.enhance a certain characteristic of an organism.)
- Inheritance, a gene is a basic unit of inheritance