exam 2 Flashcards
what is dominant
an allele that is expressed in n organisms phenotype and that simultaneously masks the effects of another allele, if another one is present
what is recessive
an allele that is expressed in an organisms phenotype if two copies are present but is masked if the dominant allele is present
what is the phenotype of an individual?
physical expression of the genotype; may be influenced by environment
example of phenotype
actual physical appearance (tall,short)
example of genotype
pair of alleles such as TT, Tt, tt
what is genotype
genetic make up of an organism; the combination of alleles for a given gene
what are chromosomes
the strand of dna found in the nucleus of eukaryotes that contain hundreds or thousands of genes
what type of observations did mendel make?
discrete physical unit was responsible for each characteristic, this unit passed from parent to offspring, and in this way the characteristic was inherited.
garden peas traits did not blend. ex: plants and their offspring were either tall or short. overtime shortplants diminished
what is allele
one or more alternative forms of a gene
what is mendelian inheritance
basic principles associated with the transmission of genetic material, forming the basis of genetics, including the law of segregation and the law of independent assortment
what is a trait?
characteristics ( tall short)
law of segregation
- monohybrid cross
- each individual has two factors for each trait
- the factors segregate during the formation of the gametes
- each gamete contains only one factor from each pair of factors
- fertilization gives each new individual two factors for each trait
law of independent assortment
- each pair of factors segregates (assorts) independently of the other pairs
- all possible combinations of factors can occur in the gametes
concept of blending
idea that parents of contrasting appearance always produced offspring of intermediate appearance
what are the Two laws that describe the behavior of genes as they are passed from one generation to the next
law of segregation and law of independent assortment
when mendel crossed a true breeding violet flowered and a true breeding white flowered plant, the offspring were
all violet
when mendel crossed a true breeding tall with a true breeding dwarf plant, all of the f1 generation were tall. therefore we may conclude that the allele for dwarfism in the pea plant is
recessive
cytogenetics ( the study of the mechanisms of heredity in the cell ) shows that mendel’s principle of segregation
is based on the separation of chromosomes during meiosis
two nontastsers for ptc will have among their offspring
nontastsers only
the blending theory is…
idea that inherited characteristics of offspring are intermediate between maternal and paternal characteristics
oogenesis differs from spermatogenesis in that oogenesis :
leads to sex cells, if fertilized, will contribute mtDNA to the zygote
begins in fetal life
usually produces only one mature ovum at any one time
the genetic information is coded by the sequence of codons. each codon is made up of 3….
nucelotides
the nuclear dna molecule controls the manufacture of proteins by the following process:
the appropriate code is copied and transported by messenger RNA to the site of protein manufacture
Somatic cells are characterized by all the following
each includes a nucleus,
they are used in multiple tissues throughout the body
each contains a complete copy of all organism’s DNA.
The genetic code is based on ….
the particular sequence of nucleotides
what is mitosis
a body cell and its nucleus divides once and produce two identical cells.
what is meiosis
a reproductive cell and its nucleus divide twice and produce four cells- two pairs of identical cells with half the number of chromosomes
what is mendelian inhertiance
Mendelian inheritance is a type of biological inheritance that follows the laws originally proposed by Gregor Mendel in 1865 and 1866 and re-discovered in 1900. These laws were initially controversial.
what is true-breeding
A true-breeding organism, sometimes also called a purebred, is an organism that always passes down certain phenotypic traits to its offspring of many generations.
what is a hybrid
the offspring of two plants or animals of different species or varieties, such as a mule (a hybrid of a donkey and a horse).
what is recessive
relating to or denoting heritable characteristics controlled by genes that are expressed in offspring only when inherited from both parents, i.e., when not masked by a dominant characteristic inherited from one parent.
what is dominant
Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus. The first allele is dominant and the second allele is recessive.
what is principle of segregation
the principle, originated by Gregor Mendel, stating that during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire one factor from each parent.
what is the principle of independent assortment
Law of independent assortment is for polyhybrid Traits i.e. More than one trait,it states that all the different traits in an organism are acquired independent of each other,they are not dependent on a particular trait
Here we are comparing the color and shape of the peas
R -round shape(dominant)
r-wrinkled shape
Y-yellow color (dominant)
y-green color
law of segregation again
Law of segregation is for monohybrid inheritance i.e. A single trait.Each parent had two alleles for a particular trait.During gamete production the two copies of each hereditary factor segregate so that the offspring acquires one factor from each parent which is in accordance to the fact that the offspring will bear only 46 chromosomes (23 from mother and 23 from father)
Here in the Punnett square we are comparing dominant T (tall) and recessive t (short ) trait
So we see 16 different possibilities because color and shape are independent of each other
bigger punnet square with lotso stuffs
what is a trait
a distinguishing quality or characteristic, typically one belonging to a person.
a genetically determined characteristic.
what is a locus
A locus (plural loci) in genetics is a fixed position on a chromosome, like the position of a gene or a marker (genetic marker). Each chromosome carries many genes; human’s estimated ‘haploid’ protein coding genes are 19,000–20,000, on the 23 different chromosomes.
what is an allele
an allele is a variant form of a gene
When the copies of a gene differ from each other, they are known as alleles. A given gene may have multiple different alleles, though only two alleles are present at the gene’s locus in any individual.
what is homozygous
having two identical alleles of a particular gene or gene
what is heterozygous
having two different alleles of a particular gene or genes.
what is autosomes
any chromosome that is not a sex chromosome.
An autosome is a chromosome that is not an allosome (a sex chromosome). … The DNA in autosomes is collectively known as atDNA or auDNA.
what is a sex chromosome
a chromosome involved with determining the sex of an organism, typically one of two kinds.
What are sex chromosomes? What determines whether a person is male or female
X and Y chromosomes; Females have two X chromosomes; males have one X and one Y chromosome
An individual has two sets of chromosomes called homologous chromosomes, having one set from his mother and one from his father. Homologous chromosomes are similar in ___.
shape, size, genetic content
What is a homologous chromosome
Homologous chromosomes are chromosome pairs (one from each parent) that are similar in length, gene position, and centromere location. The position of the genes on each homologous chromosome is the same, however, the genes may contain different alleles.
Chromosomes that have the same sequence of genes and the same structure
what is genetic recombination
the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent.
what is genetic recombination
the process by which the combinations of alleles for different genes in two parental individuals become shuffled into new combinations in offsprings individuals.
what is the human genome project
The Human Genome Project was an international scientific research project with the goal of determining the sequence of nucleotide base pairs that make up human DNA, and of identifying and mapping all of the genes of the human genome from both a physical and a functional standpoint.
what is the human genome project
A research effort undertaken to sequence all of our DNA and locate within it all of the functionally important sequences, such as genes
what is nondisjunction
the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
What is Nondisjunction and how does it occur?
If nondisjunction occurs during anaphase II of meiosis II, it means that at least one pair of sister chromatids did not separate. In this scenario, two cells will have the normal haploid number of chromosomes. Additionally, one cell will have an extra chromosome (n + 1) and one will be missing a chromosome (n - 1)
Down Syndrome: trisomy 21
It results from one of the most common chromosomal abnormalities in humans, the presence of an extra chromosome 21 in each cell or rarely part of the cells of the body.
Extra copy of chromosome 21. Down syndrome is the most common single cause of human birth defects.
usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two.
what is a somatic cell
any cell of the body except sperm and egg cells. Somatic cells are diploid, meaning that they contain two sets of chromosomes, one inherited from each parent. … a mammalian blastula in which some differentiation of cells has occurred.
any cell other than a gamete, has 46 chromosomes, body cells.
what is a gamete
A sex cell that contains the haploid of chromosomes
reproductive cells, sperm or egg
A haploid cell such as an egg or sperm. Gametes unite during sexual reproduction to produce a diploid zygote.
meiosis again
(genetics) cell division that produces reproductive cells in sexually reproducing organisms
sex cells
Gametes- sperm and egg cells. Made by meiosis with ½ the regular number of chromosomes in them.
haploid
An organism or cell having only one complete set of chromosomes
what is a zygote
The one cell that is formed when the cell accepts the sperm cell.
The fertilized egg, which is diploid, that results from the union of haploid gametes during fertilization
the fertilized egg; it enters a 2-week period of rapid cell division and develops into an embryo. (Myers Psychology for AP 2e p. 466)