Unit 6

Chromosomes:

- are rod shaped structures that contain DNA - are located in the nucleus - occur in numbers that are the same for all members of a certain species - are organized into karyotypes for scientists to analyze

Genes _______.

- are specific nucleotide sequences - are located in a specific place on a chromosome - determine the traits of an organism

----,-----, -----, and ---- are the four molecules that make up the "rungs" of the DNA structure

-Thymine -Cytosine -Adenine -Guanine

Heredity allows for ______.

-change between generations -consistency between generations

A cross involving purebred, red snapdragons and purebred, white snapdragons produce all pink offspring because both genes are present, neither being - over the other, resulting in the - of the trait.

-dominant -blending

W.S. Sutton proposed that the _____ are located on _____, and these factors segregate during _____ and the production of gametes.

-genetic factors - chromosomes - meiosis

Meiosis is associated with the _____.

-haploid number of chromosomes -gamete cells

In a dihybrid cross, the F2 will have nine genotypes, but only four phenotypes because the - genes cause the -traits to mask the - traits.

-heterozygous -dominant -recessive

Factors that can increase mutation rates are

-high temperatures -food additives -UV rays

What characteristics do mutations have?

-occasionally beneficial -omission of information -mistakes in copying

Genes are

-responsible for inherited traits -units of coded DNA -located in a specific place on a chromosome

Red-flowered snapdragons are crossed with white-flowered snapdragons, producing all pink snapdragons in the F1 generation. What would you expect if you crossed pink with pink? red, pink, white.

1/4 red 1/2 pink 1/4 white

The normal human karyotype has a total of ____ chromosomes.

46 chromosomes

The phenotypic ratio for the F2 generation in a dihybrid cross will theoretically be _____.

9:3:3:1

mutation

A change in a gene or chromosome. A change in the genetic information code

Deoxyribose

A five-carbon sugar that is a component of DNA nucleotides

Gene

A segment of DNA on a chromosome that codes for a specific trait

Gene

A segment of DNA that contains the information for making protein, and therefore allows the nucleus to run the cell's activities and carry hereditary trait

Allele

An alternative form of a gene.

Autosome

Any chromosome that is not a sex chromosome

The genetic code is carried by the _____ molecule in most organisms.

DNA

Mutations in the genetic code can occur when _____.

DNA duplicates and an amino acid is changed

The seeds collected from the first generation monohybrids are called _____.

F1

Indicate the correct designation of the paired sex chromosomes.

Male-XY Female-XX

If one parent is heterozygous white (Ww) and the other is homozygous black (ww), give the phenotype and genotype ratios for this cross. Phenotype: Genotype ratio Ww:ww

Phenotype- 1/2 white 1/2 black Ratio- 1:1

While conducting experiments on pea plants, Mendel observed that the combination of traits in the offspring did not match up with the parents. How did Mendel explain this?

The Principle of Independent Assortment

Nitrogen bases

The chemicals that make up the rungs of the DNA ladder. A-T and C-G match.

X chromosome

The sex chromosome found in both men and women. Females have two X chromosomes; males have one. An X chromosome from each parent produces a female child.

Recessive

a gene or trait that is masked when a dominant allele is present

DNA

a giant molecule consisting of the sugar deoxyribose, phosphates, and nitrogen bases; contains coded genetic information

Punnett square

a grid system used to predict possible combinations of genes due to random fertilization

Species

a group of related organisms that share features and characteristics

RNA

a nucleic acid similar to DNA that uses ribose for the sugar and the nitrogen base uracil in place of thymine

Homozygous

a pair of genes that are identical in the way they influence a trait

Heterozygous

a pair of non-identical genes that influence a trait in different ways

The genotype represents _____.

a paired combination of genes

Purebred

a phenotype (trait) resulting from homozygous genes from the offspring of true breeding

Mutation

a random error in gene replication that leads to a change

Each hereditary trait corresponds to _____.

a sequence of nitrogen bases

Darwin believed that the various species of finches on the Galapagos Islands came from one common ancestor. He believed they evolved by

adaptive radiation

dihybrid cross

breeding of individuals that have genes for two different characteristics

Environmental factors _____ affect the coding of genes.

can

Multiple alleles _____.

can interact to influence a trait, such as eye color

Dominant

can prevent the allele from being expressed in a pair of genes

Some Latin-American hummingbirds have bills that are long and curved, matching long and sharply curved flowers in their environment. The hummingbirds can easily sip nectar from the flower while conducting pollination. These two organisms may have evolved by

coevolution

Codominance

condition in heterozygotes in which both members of an allelic pair are dominant and both contribute to the phenotype

incomplete dominance

condition in heterozygotes in which both members of an allelic pair are neither dominant nor recessive to other alleles, so the two traits blend in the phenotype of the individual

Carrier

condition of being heterozygous for a recessive trait

lineage

continuous line of descent

The shark is a fish while the dolphin is a mammal. These are two completely different types of animals, but they have similar characteristics due to their similar dwellings. These animals may have evolved their similarities by

convergent evolution

Translation

converting the genetic code into the language of proteins

---- and ---- are the two molecules that make up the "rails" of the DNA structure

deoxyribose and phosphate

A monohybrid cross is made between plants that _____.

differ in only one trait

Horses, zebras, and donkeys are all different species. They are believed to have come from one common ancestor and just become more and more different due to their different environmental conditions. These animals may have evolved by

divergent evolution

Recessive genes will always be masked by dominant genes. This is Mendel's principle of

dominance

The characteristic that results from a monohybrid cross is the _____ trait.

dominant

Traits that are sex-linked are carried on _____.

either the X or Y chromosome

A gene cannot react chemically and form a trait without a proper

enzyme

Morphology

form and structure of an organism or any of its parts

All of the alleles of a specific gene in a population make up the

gene pool

sex-linked

genes that are located on the sex chromosomes

The evolutionary theory that suggests that a species slowly and continuously evolves over a long period of time is

gradualism

Haploid

having a single, complete set of chromosomes or one half of each pair of homologous chromosomes

Diploid

having chromosomes in homologous pairs

unlike alleles

heterozygous

Rr

heterozygous, dominant cell

identical alleles

homozygous

RR

homozygous, dominant cell

rr

homozygous, recessive cell

one-gene-one-enzyme concept

idea that the genetic code of the gene is responsible for the production of a specific enzyme, which regulates the metabolic pathways in the cell during meiosis; states that the combination of chromosomes in a gamete is due to chance

When the blending of traits occurs, it is referred to as the principle of _____.

incomplete dominance

rRNA _____.

is part of the ribosomes that manufacture polypeptides

Hybrid

offspring from a cross between parents; has different phenotypes for a specific trait

Each trait of a plant is determined by _____.

pair of genes

The outward appearance of a particular trait is called the .

phenotype

One gene controls the synthesis of one _____.

polypeptide

The evolutionary theory that suggests that a species can suddenly and rapidly evolve into a new species is

punctuated equilibrium

During the process of _____, two rails or sides break apart and attract new nucleotide bases to form a new and complete strand.

replication

Chromosome

rod-shaped structure that contains DNA and is located in the nucleus

Chromosomes

rod-shaped structures that contains DNA and is located in the nucleus

Mendel believed that during the formation of gametes, the pair of genes controlling a trait separate. He called this the principle of _____.

segregation

vestigial

small or underdeveloped

monohybrid cross

the breeding of two organisms that differ in a single trait

Nucleotide

the combination of phosphate, sugar, and nitrogen bases in DNA or RNA; can combine to code a specific amino acid

Phenotype

the expression of a genetic trait; what the trait looks like

Genotype

the genes present in an organism

Linkage

the presence of different genes on the same chromosome

Replication

the separation of DNA's two polynucleotide chains, each of which then acts as a template for a new chain

Y chromosome

the sex chromosome found only in males

Speciation

the spitting of a lineage into separate and distinct species

Transcription

the transfer of genetic code from DNA to an intermediary RNA molecule

The nitrogen base pairs in the DNA molecule are adenine and ------ or cytosine and ------

thymine guanine

Why did Mendel prevent his plants from self-pollinating?

to control the crossing of the traits

During the process of _____, two rails or sides break apart and pair up with RNA nucleotides, assembling mRNA.

transcription

During the process of _____, mRNA decodes information from the original DNA master plan to build proteins in the ribosomes.

translation

self-fertilization

when an organism that possesses both male and female gametes brings the two genetically identical gametes together to produce offspring

multiple alleles

when more than two alternatives for a gene exist