Ch. 14 Mendel and the Gene Idea

The number of_in a combination of alleles determine how many genos you will have for the diversity

heterozygous

The type O has what genotype? phenotype?

ii has non carbohydrate on the surface of the blood cells

The dominant allele is called like this because

it is seen in the phenotype

Is the dominant more likely to happen in all the case?

no it is not, It depends on the case

what was the name of Mendel's hypothesis?

particulate mechanism of inheritance

For any character, the observed dominant/recessive relationship of alleles depends on

the level at which examine phenotype

by linked or dependent assortment to happen you need

the locus close together on the same chromosome.

gene idea

the model that says that parents pass on discrete heritable unit-genes-that retain their separate identities in offspring

Mendel chose to track_

those characters that occurred in two distinct, alternative forms

Biologists recognized that offspring inherit _

traits form their parents

nature vs.nuture

genes vs. environment

A punnett square is a

graphical representation of mendelian probabilities.

The formula to determine how many genos for punnet square is:

2^n where "n" represents the number of heterozygous alleles

In the types of blood there is_phenotypes and_alleles representing_

-4 -3 -codominance and incomplete dominance

Each allele has a _% chance of ending up in an egg or sperm cell

-50

There is an equal chance (_%) for each egg and sperm to join forming a zygote. Thus producing an offspring from each trait has a _ (being in a gamete) times _ (joining with another gamete) chance = _

-50% -1/2 -1/2 -1/4

Mendel always saw_in dihybrid combinations. However there is a _phenotypic ration for_.

-9:3:3:1 -3:1 -each one of the two characters if you consider them separately

Locus

-A specific place along the length of chromosomes where a given gene is located -place where alleles are stored -character

Monohybrids

-An organism that is heterozygous with respect to a single gene of interest. -All the offspring from a cross between parents homozygous for different alleles are monohybrids. Ex. AA X aa produces Aa

Allele

-Any of the alternative versions of a gene that may produce distinguishable phenotype effects -Physical (show) -trait -They can be the same or different on the homologous pair of chromosomes

Pleiotropy :

-The ability of a single gene to have multiple effects on a phenotype (a single locus) (e.g. sickle cell can cause anemia, kidney failure, pain, organ and vessel damage, etc.)

The law of independent assortment

-The alleles for each trait assort independently of each other during gamete formation. -Similar to the law of segregation but dealing with multiple traits

dihybrids

-An organism that is heterozygous with respect to two genes of interest. -All the offspring form a cross between parents doubly homozygous for different alleles are dihybrids. -Ex. parents of genotypes AABB and aabb produce a dihybrid of genotype AaBb

Describe Mendel's experiment

- Purple x White flowers (P) produced offspring (F1) with all purple flowers (lost white trait) -Then Mendel took the offspring from the F1 generation and let them self-fertilize.These offspring made up the F2 generation. -Mendel suggested that if the white trait was "lost", then all the other flowers in subsequent generations would be purple. -By studying the F2 generation, Mendel discovered things that lead to his alternative hypothesis on inheritance.

Blending Theory of Inheritance

-Early Biologists believed that traits passed from parents blended together in their offspring -analogous to the way blue and yellow paints blend to make green.

codominance

-Expression of both alleles in the heterozygote -the two alleles each affect the phenotype in separate, distinguishable ways

The union of parental gametes produces _having a_. When the hybrid plants produce gametes. the two alleles_, which means_

-F1 hybrids -Pp Combination -segregate -half of the gametes receive the P allele and the other half receive the p allele

Heterozygous

-Having two different alleles for a given trait -e.g. one allele for white flowers and one for purple -heterozygous produces gametes with different alleles

Homozygous

-Having two identical alleles for a given trait -AKA... "true breeding"

Epistasis :

-Interaction between two genes where one modifies expression of the other -One character stands over the other -independent assorted -the phenotypic expression of a gene at one locus alters that of a gene at a second locus -Ex: B gene is epistatic to the C gene (b controls c) -Control cactus spines (long, short, none) -most common ratio is 9:3:3:1

Law of segregation

-Mendel's first law -the two alleles at a locus are separated during meiosis and only chance determines which will end in each gamete.

particulate mechanism of inheritance

-Mendel's hypothesis for inheritance -This model proposed that parents passed on discrete heritable units that retain their separate identities in offspring.

Trait

-One of two of the detectable variants in a genetic character -such as purple or white color for flowers

Failures in the Blending Theory of Inheritance

-Our everyday observation of the characteristics of the people -the results of breeding experiments with animals and plants -It did not explain other phenomena of inheritance, such as traits reappearing after skipping a generation.

what is the prediction of what will ultimately happen in the Blending Theory of Inheritance?

-Over generations, a freely mating population should give rise to a uniform population of individuals. -Eventually everyone would have the same traits

Mendel found that when he took a true breeding plant and crossed it with another true breeding plant (_generation) ... If they "blended" then they should_

-P generation -all of the offspring demonstrated a single trait of one of those plants.(F1 generation) -all be light purple

What were the advantages for using Pea plants for inheritance experiments?

-Pea plants have several advantages for genetics. -available in many varieties with distinct heritable features (characters) with different variants (traits). -Ability to self-pollinate or be manually cross-pollinated -short generation time and large number of offspring from each mating

Polygenic inheritance

-Several genes determine a single phenotypic trait (e.g. eye color -Additive effect of two or more genes on a single phenotypic character (cumulative effect) -Skin pigment in humans is controlled by at least three different genes. Also height -Incomplete dominance -More adaptive -quantitative character

Complete Dominance

-The DOMINANT phenotype is fully expressed in the heterozygote, masking the recessive trait (like Mendel's peas) -In such situations, heterozygotes and the dominant homozygotes are indistinguishable

Incomplete Dominance

-The DOMINANT phenotype is not fully expressed in the heterozygote -blend together -Each of the alleles have their own phenotype (original) -Because that heterozygotes have a separate phenotype, the genotypic and phenotypic ratios for F2 are the same, 1:2:1

Mendel's observations and results of his experiment

-The white trait was not lost, but merely masked by the purple flower factor (gene). -Mendel called the masked factor recessive and the expressed factor dominant -Always saw a 3:1 ratio in the F2 generation

Phenotype

-Traits that can be seen (e.g. purple flowers) - refers to physiological and as well appearance -Also behaviors

Character

-a heritable feature that varies among individuals -Ex. Flower color

quantitative character

-a heritable feature that varies coninuously over a range than in an either-or-fashion Ex: polygenic inheritance

The law of independent assortment applies to genes,_,located on_or_

-allele pairs -different chromosomes, whose are not homologous -very far apart on the same chromosome

Homozygous dominant

-both alleles are dominant -e.g. both alleles code for purple flowers

Homozygous recessive

-both alleles are recessive- -e.g. both alleles code for white flowers

Degrees of dominance:

-complete -incomplete -codominance

Monohybrid cross

-cross between heterozygous (monohybrids) -A cross between two organisms that are heterozygous for the character being followed (or self-pollination of a heterozygous plant)

When a dominant allele coexist with a recessive allele in a heterozygous, they_. It is the pathway from_to_that dominance and recessiveness come into play

-do not actually interact at all -genotype -Phenotype

Alleles can show different degrees of _and_in relation to each other.

-dominance -recessiveness

what else controls human color?

-exposure to sun -other traits

The gene is passed from_, and it does not_. Thus it retains its_even if is not_

-generations -change -identity -showing

types of homozygous

-homozygous recessive -homozygous dominant

Ex of codominance. Also this example is an example of_

-human type of blood -multiple alleles

The phenotype of two plants can be _, but the genotype can be very_.

-identical -different

Mendel's quantitative analysis of the F2 plants from thousands of genetic crosses allowed him to deduce two fundamental principles of heredity, which are_

-law of segregation -law of independent assortment

If hybrids must transmit their alleles in the same combinations in which the alleles where inherited form the P generation, then the F1 hybrids will produce_classes of gametes (_) This is the_assortment hypothesis, which predicts that the phenotypic ration of the F2 generation will be_, just as_

-only two -YR and yr -dependent assortment -3:1 -monohybrid cross

In genetics, it is important to be able to_by using_

-predict outcomes of inheritance for specific genotypes. -the punnet square doing a test cross

Punnet square

-predicts the results of a genetic cross between individuals of known genotype

Mendel's laws of segregation and independent assortment reflect the same laws of _ that apply to tossing coins or rolling dice.

-probability

The alternating hypothesis is that the two pairs of alleles _. In other words, genes are_

-segregate independently of each other -packaged into gametes in all possible allelic combinations, as long as each gamete has one allele for each gene.

A Punnett square can be used to determine an unknown genotype by doing a_by determining the_

-test cross -appearance of the offspring Ex: purple plants that could have either homozygous dominant alleles or heterozygous alleles

norm of reaction

-the range of phenotypes produced by a single genotype, due to environmental influences. -Ex: color of flowers depending acidity and aluminum content of the soil, and persons' blood count depending on such factors as altitude, customary level of of physical activity, and the presence of infectious agents.

While creating the second law, Mendel reasoned that if all the traits in the pea plants were joined together, then when he crossed_. Instead he obtained_.This means_

-two different traits (called a di-hybrid cross) he would get the same ratio as if it were a single trait (mono-hybrid cross = one trait) 3:1 -a ratio of 9:3:3:1 -traits (alleles) were independent of each other

Mendel's 4 hypothesis consisted of:

1) Alternative forms of genes are responsible for variations in inherited characters (called alleles). -These alleles occur at the same position (locus) on the chromosome 2) For each character an organism inherits two alleles (one from each parent) On homologous chromosomes 3) If the two alleles (traits) are different, one is fully expressed (dominant) and the other is completely masked (recessive) 4) The two alleles for each character segregate during gamete production (meiosis), ending in different gametes (sperm or egg) -If different alleles are present in the parent, then: -There is a 50% chance that a gamete will receive the Dominant Allele -There is a 50% chance that a gamete will receive the Recessive Allele -This is Mendel's first law, the law of segregation.

Mendel identifies his second law of inheritance by following _

2 characters at the same time.

How large a punnet square would you need to draw to predict the oofsprings of a self-pollination of trihybrid (YyRrLl)?

8X8= 64 possible offspring

Who disputed the idea of Blending Theory of Inheritance?

A monk called Gregor Mendel

The type A blood has what genotype? phenotype?

AA or Ai has the type A carbohydrate on the surface of the blood cells

What type of blood is the universal recipient?

AB

The type AB blood has what genotype? phenotype?

AB has both type A and B carbohydrates on the surface of the blood cell

Genotype

An organisms genetic make-up (e.g. alleles (PP))

the type B blood has what genotype? phenotype?

BB or Bi has the type B carbohydrate on the surface of the blood cells

How did Mendel studied inheritance?

By breeding garden peas

How can scientist study patterns of inheritance?

By crossing two true-breeding varieties of an organism

All alleles are _ when examined at the DNA level.

CODOMINANT

Then he crossed the F1 generation between each other to obtain _generation

F2

hybridization

In genetics, the mating, or crossing, of two true-breeding varieties.

Multiple alleles :

It is possible to have more than two forms of an allele

Because incomplete dominance is blending, does it provide evidence for the blending hypothesis?

No, the reason is that the blending hypothesis states that the red or white trait (in this case) would never be retrieved from the pink hybrids. In fact, interbreeding F1 hybrids produces F2 offspring with a phenotypic ratio of 1 red: 2 pink: 1 white.

what type of blood is universal donor?

O

When do alleles independently assort during meiosis?

Prophase in meiosis I by crossing over process

true breeding plant

a plant that always produced the same plant when self-fertilized

how AB blood shows codominance?

both type A and B carbohydrate, fully equally expressed on the surface

dihybrid cross

cross between two organisms that are each heterozygous (dihybrids) for both of the characters being followed (or self-pollination of a plant that is heterozygous for both characters)

gene

discrete heritable unit of inheritance

The capital letter in the punnet square represents

dominant allele

The characters of Mendel's pea plants were simple because

each character is determined by one gene, for which there are only two alleles, one completely dominant and the other completely recessive.

Another departure from simple Mendelian genetics arises when the phenotype for a character depends on _ as well as genotype.

environment

Mendelian genetics (mendelism), its basic principles of segregation and independent assortment apply_

even to more complex patterns of inheritance.

cross-pollination

fertilization between different plants

Alleles are variations in_

gene's nucleotide sequences

Phenotype

physical manifestation of the genotype

what is the contrary of pleiotropy?

polygenic inheritance

According to Mendel's idea, during self-pollination of plants, gametes of each class unite

randomly

The lower case letter in the punnet square represents

recessive allele

gamete

sperm or egg

The explanation of heredity most famous during 1800s was

the blending hypothesis

what is the alternative to the blending model?

the gene idea