patterns of inheritance and meiosis chap 9 and 10 BIO I

Genetics explains and predicts?

inheritance patterns

Most genes encode proteins that have nothing to do with outward

appearance. The enzymes essential to our lives are also the

products of?

genetics.

Studying genetics also allows scientists to breed superior crops

and doctors to track genetic illnesses.

Recall that a chromosome is a piece of DNA containing many different genes. Each gene’s ___ is its location on a chromosome

locus

When two haploid sex cells fuse during fertilization a __ zygote with two full sets of chromosomes is formed.

diploid

Each chromosome is a member

of a ___ of chromosomes

homologous pair

diploid cells hace —’ alleles for each gene

two

members of a homologous pair have the same genes but might have different versions or === of those genes

alleles

are alleles always identical

No, they may differ in form.

How do meiosis, fertilization, diploid cells, and haploid cells

interact in a sexual life cycle?

Meiosis produces haploid gametes from diploid cells, which then fuse during fertilization to form a new diploid organism, continuing the sexual life cycle.

Gregor Mendel uncovered basic laws of?

inheritance through pea plant experiments.

explain medels experiment, what were the results

Mendel's experiments involved cross-breeding pea plants with distinct traits to observe inheritance patterns across generations, leading to the formulation of his laws of segregation and independent assortment.

true breeding plants

self fertilization yields offspring with same seed color as parent plant

hybrid plants outwardly resemble true breeders but produce?

mixed offspring

__ alleles exert their effects whenever they are present crossing a yellow-seed plant with a green-seed plant always yields some yellow seeds

Dominant

A ___ allele, like green seed color, is one whose effect is

masked if a dominant allele is also present.

Recessive

Recessive alleles usually encode ___ proteins.

nonfunctional

Why do some plants produce both yellow and

green seeds?

The answer has to do with each plant having two alleles for each

gene (because of their homologous pairs of chromosomes). If one allele is dominant and the other recessive, the dominant trait may be expressed alongside the recessive trait, leading to mixed seed colors.

A genotype represents an individual’s ___ for ____

two alleles, for one gene

The genotype confers a ___ which is the physical

appearance—for example, an observable characteristic such as

seed color.

phenotype

homozygous dominant

individuals have two dominant alleles for a gene

heterozygous individuals

have one dominant and one recessive allele

homozygous recessive

individuals have two recessive alleles for a gene

can individuals with the same phenotype have different genotypes?

Yes, individuals can exhibit the same phenotype but have different genotypes, a condition known as phenotypic variance.

The seed color gene encodes a ____ enzyme

pigment-metabolizing

The seed color gene encodes a pigment-metabolizing enzyme.

The dominant allele, Y, is active and produces yellow color; the

recessive allele, y, is inactive.

In the absence of enzyme activity the seeds ?

will be green in color.

Distinguish between dominant and recessive, heterozygous and

homozygous, phenotype and genotype

Dominant alleles mask the effect of recessive alleles, heterozygous individuals have two different alleles for a trait while homozygous individuals have two identical alleles, phenotype is the observable trait and genotype is the genetic makeup.

Punnett squares represent?

gamete formation

and fertilization

a punnet square uses what?

the genotypes of the parents to reveal which alleles the offspring may inherit

in this example a female parent heterozygous Yy for seed color is crossed with a male parent also heterozygous Yy for seed color, this is a ____ since both parents are heterzygous

monohybrid cross

do punnet squares show how alleles sepeate or come together during meiosis?

seperate

When germ cells divide by meiosis, the gametes receive how many alleles per gene?

one allele per gene.

For the seed-color gene, there is an equal chance of receiving?

either the dominant or recessive allele.

© McGraw Hill 20

Punnett squares show how the alleles get back ___ at fertilization

together

This Punnett square is a prediction that shows the

relative proportion of the offspring phenotypes and genotypes.

Offspring can reveal parental genotypes

homozygous dominant

If a cross between a yellow seed pea plant (YY or Yy) and a green-seed pea plant (yy) yields all yellow seeds, the yellow- seed parent is homozygous dominant.

offspring can reveal parental genotypes: heterozygous

If a cross between a yellow-seed pea plant (YY or Yy) and a green- seed pea plant (yy) yields some green seeds, the yellow-seed parent is heterozygous

the two alleles for the seed color gene are packed into separate which are then combined at___

gametes; fertilization

Cystic fibrosis is caused by a recessive allele. If a healthy carrier

and an affected individual have a child, what is the chance the

child will be affected?

A. 1/4

B. 1/3

C. 1/2

D. 3/4

E. 1

1/2

Use the following terms to explain how parents can be disease

carriers:

• Allele

• Genotype

• Phenotype

• Dominant

• Recessive

Parents can be carriers of diseases when they possess a recessive allele in their genotype that does not manifest in their phenotype due to the presence of a dominant allele. This means one parent may express a dominant trait while carrying a recessive allele for a genetic disorder, thereby passing it to offspring.

This Punnett square

is a prediction that

shows the relative

proportion of?

phenotypes and

genotypes.

Figure 10.6Access the text alternative for slide images.

Dihybrid crosses track the inheritance of __ genes at once

two different

__ on different chromosomes can be combined into one

large Punnett square.

two genes

during what process do alleles seperate

during meiosis

Based on dihybrid crosses, Mendel proposed the law of independent assortment which is?

the segregation of alleles for one gene

does not influence the segregation of alleles for another gene

Why doesn't the Punnett square below include a female gamete

with genotype rr?

A. Each germ cell only has one r allele.

B. The y allele is dominant to the r.

C. The r alleles separate during meiosis.

C. The r alleles separate during meiosis.

what is the prdouct rule what proble is it solving?

The product rule states that the probability of two or more independent events occurring together is the product of their individual probabilities. It is used to calculate the likelihood of specific combinations of alleles in offspring.

the product rule ___ individual probablities together

multiplies the

The probability that an offspring inherits genotype Rr Gg Tt =

probability of Rr x the probability of Yy x probability of Tt

A male with genotype Qq Bb Dd is crossed with a female with

genotype qq bb dd. What proportion of the offspring will be

homozygous recessive for all three genes?

A. 1/2

B. 1/3

C. 1/4

D. 1/6

E. 1/8

1/8

How does the law of independent assortment reflect the events of meiosis?

It states that alleles for different traits segregate independently during gamete formation, reflecting the random assortment of chromosomes during meiosis.

Genes close together on the same chromosome

are ___

linked

Punnett squares and the product

rule assume:

• two genes are sorting independently.

• When genes are linked, they are physically near each other.

• Therefore, they do not sort independently.

• The linked genes are not inherited independently of each other.

Punnett squares and the product

rule cannot be used if genes are?

linked, because inheriting one allele influences the likelihood of inheriting a linked allele

Genes can become ___ during cross over

unlinked

crossing over physically seperates the two gene loci onto how many different chromosomes?

two different chromosomes

Very close genes are ___ by crossing over

less affected

The probability of a crossover event occurring between two linked alleles is ___ to the distance between the genes

directly proportional

Crossover events are counted by

tallying

offspring in which the genes are inherited

separately.

Crossover frequencies are used to find the relative

position of genes The letters below the linkage map of this chromosome represent

different gene loci. The numbers above represent crossover

frequencies relative to gene y

Explain how to use crossover frequencies to make a linkage map.

Crossover frequencies can be utilized to estimate the relative distances between genes on a chromosome by measuring the frequency of recombination between them. By calculating these frequencies, researchers can create a linkage map that visually represents the arrangement of genes.

what are alternative patterns of inheritance

Alternative patterns of inheritance refer to non-Mendelian inheritance patterns that include phenomena such as incomplete dominance, codominance, epistasis, and polygenic inheritance, which can affect how traits are transmitted from parents to offspring.

Dominant alleles masked recessive alleles in the genes

Mendel studied, creating patterns of

phenotypic and

genotypic ratios.

In other genes, alleles interact differently. This changes the nature of the

phenotypes, but not the genotypes.

In incomplete dominance:

the heterozygote has an intermediate

phenotype. Here, the red allele does not mask the white allele—if it did, heterozygotes would appear red.

Incompletely dominant alleles create a

blended

heterozygote phenotype When the red allele (r1) and white allele (r2) are both present, the heterozygote (r1r2) phenotype is an intermediate pink. The white allele encodes a nonfunctional pigment protein

what is codominant alleles?

Alleles that express both traits fully in a heterozygote. For instance, in a flower with red and white alleles, both colors may be present in the petals. they do not mask each other, and have more than one allele that encodes a functional protien

Codominant alleles create

double phenotype

Codominant alleles create a double phenotype

If two dominant alleles are present, both proteins encoded by

those alleles will be represented in the phenotype.

Human blood type alleles A and B are

codominant

In human blood

types, both IA and

IB are

dominant alleles

Genotype IA IB

Confers red blood

cells with

both A

and B molecules

Human blood type alleles A and B are both dominant

over the O allele true or false

True

The I gene also has

a recessive allele,

i, which encodes a

non-functional

protein.

But the two

dominate alleles IA

and IB, make

the

I gene codominant

pleiotropy

one gene has multiple effects on the phenotype. For

example, a gene might affect more than one biochemical pathway.

Products of different genes can interact with each other

Section Epistasis

occurs when one gene’s product affects the expression of another gene. Expression of the h allele (gene 1) affects the expression of A and B alleles (gene 2).

How do pleiotropy, epistasis, incomplete dominance, and

codominance increase the number of phenotypes

by altering the effects of genes on traits, allowing for a greater variety of expressed characteristics in offspring.

Sex-linked genes have unique inheritance patterns. In humans, females have two X chromosomes (XX). Males have one X chromosome and

one Y chromosome (XY). This can lead to traits on the X chromosome being expressed differently in males and females.

This Punnett square shows

that each fertilization event

has a

50% chance of producing

a female and a 50% chance of

producing a male.

Which gamete determines the sex of the offspring?

The egg will always carry an

X

chromosome.

The sex chromosome in the

sperm therefore determines if

the offspring is female or male.

males only have one allele for genes on the?

X chromosome

whichever allele males have on their single X chromosome is the one that expresses as their..?

phenotype.

females have two x chromosomes the interation of the two alleles determines the?

phenotype for traits linked to the X chromosome. `

recessive disorders effect more males or females?

males due to their single X chromosome. Males only need to inherit one X-linked recessive allele to express the recessive disorder. Females must receive a recessive allele on both X chromosomes to express the recessive disorder, which is less likely to occur.

Hemophilia is an X-linked recessive disorder. If an affected female

(has the disease) and an unaffected male (does not have the

disease) have a boy, what is the chance he will have hemophilia?

1

x linked disordersq

look at image

X-inactivation prevents double dosing of gene products

Each cell in an XX

individual, such as

these female cats,

randomly

inactivates one X

chromosome

X-inactivation produces unique inheritance patterns

f one X chromosome has an allele for orange fur, and the other has an allele for black fur, color patterns emerge when X chromosomes are randomly inactivated.

X-linked dominant disorders are less severe in female

In humans, an X-linked

disorder called Rett

syndrome is lethal to

boys and has varying

effects on girls,

depending on how

many cells inactivate

the X chromosome

carrying the Rett allele.

Why do males and females express recessive X-linked alleles

differently?

Males express recessive X-linked alleles more frequently because they have only one X chromosome, while females have two, which can result in one dominant allele masking the recessive allele.

A pedigree depicts

family relationships and phenotypes

© McGraw Hill 72

Pedigrees show modes of?

inheritance and can reveal patterns of genetic conditions within families.

This pedigree tracks an autosomal dominant disorder. What is

the genotype of I-2?

It is most likely heterozygous (Aa) if the phenotype is expressed.

How are pedigrees helpful in determining a disorder’s mode of

inheritance?

They provide a visual representation of family relationships and phenotypes, showing how traits are passed through generations.

can the enviroment alter phenotype?

Yes, environmental factors can influence an organism's phenotype by affecting gene expression and interactions.

Epigenetics is a

field of research that explores how cells adjust gene expression without altering underlying DNA sequence. Differences in lifestyle and experience can epigenetically influence gene expression and alter the chances of cancer, depression,alcoholism, and type 2 diabetes for some people.

Some traits depend on multiple genes Skin color is a

polygenic trait; it is

affected by more than one gene

How can the environment affect a phenotype?

The environment can alter a phenotype by influencing gene expression through factors such as diet, temperature, and exposure to toxins.

homozygous vs heterozygous

Homozygous refers to having two identical alleles for a particular gene, while heterozygous refers to having two different alleles for that gene.

genotype vs phenotype

Genotype refers to the genetic makeup of an organism, while phenotype refers to the observable traits and characteristics resulting from the interaction between the genotype and the environment.

Dominant vs recessive

Dominant alleles mask the effects of recessive alleles in determining an organism's phenotype. A dominant trait will be expressed if at least one dominant allele is present, whereas a recessive trait only appears if both alleles are recessive.