genetics Flashcards
what is genetics
the branch of biology concerned with heredity and variation of inherited characteristics (the transmission of genetic info from parent to off spring)
who is hippocrates
greek an ancient greek physician father of medicine
what is pangenesis
particles called pangenes travel from each part of an organisms body to the egg/sperm and are then passes to the offspring
something to do it hippocrates
who is Aristotle and his discoveries
-greek philosopher and naturalist
-what is inherited was fromed from blood rather than particles of the features themselves. the “vital heat” from the blood had the capacity to produce offspring of the same form not because it already contained all the parts in miniature
who is responsible for the very beginning of genetics and roughly when was this
500 B.C - 322 B.C
hippocrates and aristole
who are some people involved in the dawn of modern biology in relation to genetics and when was this err
1600-1850
William harvey
john dalton
louis pasteur
carolus linnaeus
jean-baptiste Lamarck
charles darwin
who was william harvey and what was his descovery
an english anatomist
the theory os epigenesis- an organism is derived from substances present in the egg which differentiate into adult structures during embryonic development
who was john dalton and what did he discover
english chemist/physicist in 1808
all matter is composed of small invisible units called atoms
what did louis pasteur did discover
the germ (cell) theory
all organsims are composed of basic visible units called cells which are derived from simular preexisting structures
what did carolus Linnaeus discover
the fixity of species
members of a species can give rise only to other members of the species thus implying that all species are independently created
what theory did jean-baptiste lamarack discover
the inheritance of acquired characteristics
nature produced successively all the different forms of life on earth, and environmentally induced behavioral changes lead the way in species change
what theory did charles darwin discover
the theory of the origin of species
the species arose by decent with modification from other ancestral species
what were two concepts that were widely accepted during the dawn of modern biology in relation to genetics (1600-1850)
-“bending” theory of inheritance
-inheritance of acquired characteristics
what is the blending theory of inheritance
the genetic materials contributed by the male and female mix in forming offspring and the progeny inherits any characteristic as the average of the parents values of that characteristic
what was the concept of inheritance of acquired characteristics
it was believed that an organism acquires some traits during its life time and they are then passed onto the offspring
who and how was the principles (basic role) of inheritance first demonstrated by
gregor johann mandel, an austrailian monk who bred pea plants
what are some examples of gregor johann mandel work
-he first demonstrated the principal of inheritance
-he was the first scientist to effectively apply quantitative methods to the study of inheritance
-his major discoveries including those known as mandels principles of segregation and independent assortment became the foundation of the science of genetics
why did mandel choose pea plants for his experiment
-pea plants can easily be cultivated in the garden
-pea plant has many varieties with distinguishable heritable features or characteristics (traits)
how would you manually cross pollenate pea plants
1) remove stamens from purple flower
2) transfer pollen from stamen of white flower to the stigma of a purple flower
what is a phenotype
-it refers to the physical appearance of an organism
-observable/expressed trait or traits of an individual including the organisms appearance, development, biochemical and physiological properties and behavior
what is a genotype
-it refers to the genetic make up of an organism
-in a more narrow sence the term can be used to refer to the alleles or variants of a gene, that are carried by an organism
what are the three factors that determine phenotye
-genotype
-non-inherited environmental factors
-epigenetic factors
describe mandels experiment called monohybrid cross
he first performed experiments to determine the pattern of inheritance of single traits. such exparaments are called monohybird cross
what are the seven traits that mandel chose
flower shape, color, flower position, seed color, seed shape, pod shape, pod color, and plant height
what is cross (hybridization)
the cross-fertilization of two different varieties/species
what is a hybrid
the offspring of parents (P generation) of two different varieties/species
what is the F1 generation
the first generation resulting from a cross
what does F1 stand for
F stands for filial and F1 for first filial
what is the P generation
-its the true breeding parents
-true breeding lines are a genetically pure line of organism; organisms for which sexual reporduction produces offspring with inherited trait(s) identical to those of parents
if you cross a purple and white flowered pea for the P generation what colour would the offspring be
all would be purple
what is the F2 generation
the next generation of plants form self fertilization of the F1 offspring
if you had a purple and white pea plant flower in the P generation and then a purple in the F1 what could the F2 generation be
-it could produce both purple and white plants
-there would be a ratio of appx 3:1 purple:white
when mandel tested all 7 traits in all cases F1 generation only one of the two traits was expressed, and in F2, 75% of the generation was the same as in F1 ad 25% in the other. what did he conclude because of this
-for each trait there is a pair (alleles) of heritable factors (what we now call genes) in parents
-during the formation of gametes (F or M cells) the two factors for a trait separate, and only ie factor is passed onto a gamete
-when F or M gametes fuse during fert each parent contributes one of those factors for a trait so that the offspring has a pair of factors
-far a cross between individuals with different traits of a pair factors for both traits are present but one is masked by its partners
what are alleles
althernative forms of a gene; genes governing variation of the same character that occupy corresponding positions (loci) on homologus chromosomes
what does homozygous mean
a true breeding organism having two identical alleles for a given characteristic
what does heterozygous mean
having two different alleles for a given charicteristic
what is hemizygous
a condition in which only one copy of a gene or DNA sequence is present in diploid cells
what is a dominant allele
an allele that is always expressed when it is present, regaurdless of weather its homo or heterozygous
what is a recessive allele
and allele that is not expressed in the heterozygous state
what does a punnett-square explain
mandels hypothesis at the genotypical level
what is testcross
-a cross of an individual of unknown genotype (which may be ether hetero or homozygous) for a particular characteristic with a homozygous-recessive individual for that same characteristic
-BREEDING THE MYSTERY INDIVIDUAL WITH A HOMOZYGOUS RECESSIVE INDIVIDUAL
what is a dihybrid cross
a genetic cross in which parents differ with respect to the alleles of two loci of intrest
why did mandel preform his two trait cross experiment
to see if the two traits of a parent are pass on together in gametes or whether they segregated independently
if two gametes joined and they were YYRR for yellow round and yyrr green wrinkled what are the possibilities of each generations colors
-F1 would be YyRr and would be yellow round
-F2 would be 9 yellow/round : 3 yellow/wrinkled : 3 green/round : 1 green/wrinkled
what is the ratios of two trait cross
9:3:3:1
what arevariations of mandels law
co dominance and incomplete dominance
pleiotrphy
epistasis
polygenic inheritance
what is mandels second law
the law of independent assortment
alleles of two (or more) different genes get sorted into gametes independently of one and other
what is incomplete dominance
a type of inheritance in which one allele for a specific trait is not completely expressed over its paired allele in F1 hybrids. this results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles
ig.. a purple and white flower create a pink one
what is codominance
a cross between organisms with two different phenotypes produce offspring with a third phenotype in which both of the parental traits appear together
i.g.. coat colours in cattle, dogs and horses follow the codominance inheritance
what is multiple alleles
occurrence of a gene that exists as three or more alleles in a population
i.g… the 4 ABO blood groups in humans are determined by 3 enzyme (I) that attaches A or B carbohydrates to make IA, IB, and i
how is the 4 phenotypes of ABO blood groups in humans determined
by three alleles for enzymes (I) that attaches A or B carbohydrates to red blood cells: IA, IB and i
what is pleiotrophy
the determination of more than one character by a single gene
i.g sickle cell anemia
what is epistasis
occurs when two or more different gene loci contribute to the same phenotype but not additively. it is often described as when one gene masks or modifies the phenotype of a second gene
i.g coat colors in mice
where are genes located
on the chromosome
what behavior accounts for mandels principle of inheritance
behavior of chromosomes during meiosis
what is the behavior of chromosome s during meiosis for mandels princapals
-diploid individuals, as in animals or plants, posses two sets of homologous chromosomes
-two chromosomes bear two alleles (the same or different) at the same positions
-each set comes from male or female parent
-when any individual produces gametes the alleles separate so each gamete receives only one member of the pair of alleles
what is bateson-punnentt’s exparament
-he used two traits in sweet peas. flower colour and pollen shape
-one parent homozygous dominant purp flower (PP) and long pollen grain (LL) and another parent homozygous for recesive red flower (pp) and round pollen grains(ll)
what was the results of bateson-punnetts exparament for the cross of heterozygous plants (PpLl)
they expressed dominant traits- purple flower and long grain
what were the results of the F2 generation for dihybrids crosses for bateson-punnent square exp
-single trait segregated following mandels segregation principle producing a phenotypic ratio of roughtly 3:1
-two trait segregation did not produce the 9:3:3:1 ratio that is predicted for a dihybrid cross
-instead a larger proportion of plants with purple flower (P) and long pollen (L) (75%) and red flower (p) round pollen (l) (15%) were observeed
what are the two trait segregation ratios of bateson vs mandels experiments
bateson: 15.6 : 1 : 1.4 : 4.5
mandels: 9 : 3 : 3 : 1
what is the explanation of the ratios found in batesons punnent exparament for the F2 generation of dihybrid crosses
-genes for the two traits may not be seggregated evenly in all the gametes formed
-in this experiment meiosis in herterozygous (PpLl) pea plant produced two predominant types of gametes (PL and pl) rater then equal number of 4 types of gametes formed
-it was revealed that the dominat genes for purple color and long pollen are located on the same parental chromosome
do genes generally follow mandels principal of independent assortment
-no
-in an organism each chromosome possesses many genes
-during meiosis close localized genes on a chromosome tend to be passed on together to a gamete
-the genes that are located close together on the same chromosome are linked and called linked genes
what are linked genes
genes that are located close together on the same chromosome which are linked
in batesons punnent exparament for the F2 generation of dihybrid crosses what about the less number if plants with purple round and red long traits
-recombinants
-some Pl and pL gametes were also formed
-crossing over accounts for the recombinant gamete formation and recombines liked genes into assortment of alleles not found in parents
what is crossing over
the exchange of segments between chromatids of homologous chromosomes during the prophase 1 of meiosis 1
what is a linkage map
using segregation rations to predict recombination freaquncies (precent of recombinats) linkage maps could be developed to help determine the position of different gene loci on the chromosome
what is unit of a linkage map called
map unit is equivelent to a recombinant offspring freaquency of 1%
the map unit is also called the centimorgan
what is morgan genetics— the chromosomal basis of inheritance
-morgans results revealed that if many traits are on the same chromosome it contradicted mandels claim of independence of assortment
-morgan confirmed the chromosomal theory of inheritance that genes carried on the same chromosome follow the mechanism basis of heredity
how is the sex of an organism determined
by one chromosome- the sex chromosome
do all species have the same and same amount of sex chromosomes
no they can have different numbers and different kinds
what sex chromosomes do humans have
females have XX males have XY and all gametes have X.
is it the male or female in humans that determines the sex
the male
in insects such as grasshoppers and flys how do sex chromosomes determine gender
-females have XX but male has only one X
-Y chromosome is absent
in fish and birds how do sex chromosomes determine gender
male is XX (called ZZ) and female is XY (ZW) so the situation is opposite from humans. so the female (egg) determines gender of offspring
in insects such as bees and ants how do sex chromosomes determine gender
-sex is determined by chromosome numbers
-female develops form the fertilizeed egg chromosome numbers while male develops from the unfertilized egg (halploid)
what is an autosome
any chomosome that is not a sex chromosome
what could happen if human individuals has abnormal sex chromosomes
they could be physically normal but be starile
what are human individuals with XO chormosomes like
females who could be physically moderately abnormal and mentally normal, but sterile (called turners syndrome)
what are human individuals with XXY chromosomes like
they are male individuals who could be physically normal but always sterile (kinefelter syndrom)
how common is XYY and what is it called
it occurs in 1 in 1000 male births. its called jacobs syndrome
what are human indviduals with XYY chromosomes like
births show normal clinical sighs and most males with 47 chromosomes (XYY) have normal sexual development and have normal fertility
are most of the genes on sex chromosomes for sexual traits
no most arent
in humans how many genes are contained on the Y chromosome and the X chromosome
-less then 200 genes are found on the Y chromosome, among them are the male determinants
-X chromosomes contain a large number of genes (over 1000 genes)
why is color blindness, muscular dystrophy and hemophilia more prone in men
-chromosomes exist in homologous pairs in a diploid organism
-males however contain a single X and Y
-several important human diseases are inherited as X liked recessive
-making it more frequent in men then women
what is hemopheillia
a mostly inherited genetic disorder that impairs the bodys ability to make blood clots, because it lacks sufficent blood clotting proteins (clotting factors)
