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