Chapter 11 Mendel nd the Gene

What are genes?

Segments of DNA coding for proteins that determine traits.

How do offspring inherit genes from their parents?

Offspring receive half of their genes from their mother (egg) and half from their father (sperm).

What is the human life cycle's initial stage?

The fertilized egg cell, or zygote, formed by the fusion of haploid gametes.

What are alleles?

Different versions of a gene that can affect the same character.

What is the difference between genotype and phenotype?

Genotype is the genetic makeup of an individual, while phenotype is the observable traits.

What is the Law of Segregation?

The principle stating that the two alleles for a heritable character separate during gamete formation.

What is the significance of dominant and recessive alleles?

Dominant alleles show their effect even if only one copy is present, while recessive alleles show their effect only when two copies are present.

What does natural selection imply?

Organisms better adapted to their environment will survive and reproduce, shifting allele frequencies over time.

What is a character in Mendel's study?

A heritable feature that varies among individuals, such as flower color.

What is a trait?

A variant for a character, such as purple or white color for flowers.

What is a monohybrid cross?

A genetic cross involving a single trait where both parents are heterozygous.

What did Mendel's F1 generation results show?

All F1 hybrids had purple flowers, indicating the dominance of the purple flower trait.

What was the ratio of traits in Mendel's F2 generation?

A 3:1 ratio of purple-flowered to white-flowered plants.

What is a test cross?

A cross used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive.

What is the role of Punnett Squares?

They are used to predict genotype ratios in genetic crosses.

What did Mendel conclude about the inheritance of traits?

Traits are inherited independently and can be masked by dominant alleles.

What is the significance of Mendel's publication?

His work was largely ignored until 1900, when other scientists rediscovered his principles of heredity.

What is the genetic makeup of an individual referred to as?

Genotype.

How did Mendel ensure the purity of his breeding experiments?

By using true-breeding plants that produce offspring identical to themselves.

What happens during gamete formation according to Mendel's model?

The two alleles for a heritable character segregate into different gametes.

What is the observable characteristic of an organism called?

Phenotype.

What is the outcome when true-breeding yellow seed plants are crossed?

All offspring will have yellow seeds.

What does it mean for an allele to be dominant?

It means the allele's effect is expressed even if only one copy is present.

What is the result of crossing two heterozygous parents in a monohybrid cross?

The offspring will have a mix of genotypes, including homozygous dominant, heterozygous, and homozygous recessive.

What does the term 'selective pressure' refer to?

Environmental factors that influence which individuals survive and reproduce.

What is the significance of the 3:1 ratio observed in Mendel's experiments?

It indicates the presence of dominant and recessive traits in the offspring.

What does it indicate if offspring display a recessive phenotype?

The mystery parent must be heterozygous.

What is a testcross?

Breeding an individual with a recessive homozygote to reveal the genotype of that organism.

In a cross between round seeds (dominant) and wrinkled seeds (recessive), what would the offspring's genotypes be if 50% display the wrinkled phenotype?

The parent genotypes are Round seed: Rr, Wrinkled seed: rr.

What does the Law of Independent Assortment state?

Each pair of alleles segregates independently during gamete formation.

What is incomplete dominance?

A situation where the phenotype of F1 hybrids is a blend of the parental traits.

What is codominance?

A condition where both alleles in a heterozygote are fully expressed in the phenotype.

What is the significance of multiple alleles in genetics?

Most genes exist in populations in more than two allelic forms, affecting traits like blood type.

What are the phenotypes of the ABO blood group in humans determined by?

Three alleles: Iᴬ, Iᴮ, and i.

What is pleiotropy?

A property where one gene has multiple phenotypic effects.

What is the inheritance pattern of cystic fibrosis?

It is caused by a recessive allele, and carriers are phenotypically normal.

What is the probability of two carriers mating if a recessive allele is rare?

The chance is low unless they are consanguineous.

What is the effect of a lethal dominant allele?

It can cause death before reproduction but may be passed on if symptoms appear after reproductive age.

What is epistasis?

When the expression of one gene depends on another gene.

What is a polygenic trait?

A trait that is affected by more than one gene, resulting in continuous variation.

How does crossing over affect linked genes?

The chance of crossover increases as the distance between two linked genes increases.

What happens when genes are physically near each other on a chromosome?

They do not assort independently and are inherited together.

What is the expected ratio of genotypes in a dihybrid cross?

1:2:1:2:4:2:1:2:1.

What is the result of breeding two gold-spotted salamanders according to the iClicker question?

It will produce only gold-spotted offspring.

What is the genotype of a normal individual with cystic fibrosis?

Homozygous for the non-functional CFTR allele.

What is the genotype of a carrier for cystic fibrosis?

Heterozygous for the CFTR allele.

What is the inheritance pattern of achondroplasia?

It is caused by a rare dominant allele.

What is the phenotype of individuals with Huntington's disease?

They show no symptoms until about 35-45 years of age.

What is the probability of inheriting a recessive disorder?

It shows up only in individuals who are homozygous for the recessive allele.

What are carriers in genetics?

Heterozygous individuals who may transmit a recessive allele but are phenotypically normal.

What is the significance of consanguineous matings in genetics?

They increase the chance of mating between two carriers of the same rare allele.

What does the term 'linked genes' refer to?

Genes that are inherited together because they are physically near each other on the same chromosome.