Inheritance and Genetics Flashcards
the transmission of traits from parents to
offspring
Heredity
the scientific study of heredity
Genetics
a heritable feature that varies among individuals
within a population
Character
a variant of a character found within a
population.
Trait
the expressed traits of an organism
Phenotype
the genetic information for a particular trait
Genotype
the offspring of two parents that differ in one or more
inherited traits; an individual that is heterozygous for one or more pairs of genes.
Hybrid
aka hybridization; the cross-fertilization of two different varieties of an organism or of two different species.
Cross
parental; the individuals acting as parents from which
offspring are derived in studies of inheritance
P Generation
first filial; the offspring of two parental (P generation)
individuals.
F1 Generation
second filial; the offspring of the F1 generation.
F2 Generation
a mating of individuals differing at one genetic locus.
Inheritance of only one character is studied
Monohybrid Cross
the unit of inheritance; a segment of DNA that encodes a protein sequence
Gene
alternative versions of genes that account for variations in inherited characters
Allele
having two identical alleles for a gene
Homozygous
having two different alleles for a gene
Heterozygous
In a heterozygote, the allele that determines the
phenotype with respect to a particular gene
Dominant Alleles
in heterozygotes, the allele that has no noticeable effect on the phenotype.
Recessive Allele
a trait or allele that is most common in nature.
wild type
the full complement of genes encoded by an organisms DNA
Genome
Before Mendell, scientists incorrectly believed that the process of inheritance involved _________
Continuous variation
- Parents pass on to their offspring discrete inheritable factors
- genes retain their individual identities generation after generation
-genes may be sorted, but retains their intact identities
Discontinuous Variation
Parental genes are randomly separated
to the sex cells so that sex cells contain only one
gene of the pair. Offspring therefore inherit one
genetic allele from each parent when sex cells
unite in fertilization
Law of Segregation
genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another
Law of independent assortment
when a trait is the result of the expression of
several genes.
Polygenic inheritance
genes located near each other on the same
chromosome that tend to travel together during
meiosis and fertilization. They are often inherited as a set
Linked Genes
a gene located on a sex chromosome. The
human X chromosome contains approximately
1,100 genes, whereas the Y chromosome
contains only 78, about half of which are
expressed only in the testes
Sex-linked Gene
Genes are located at specific positions (loci) on chromosomes and the behavior of chromosomes during meiosis and fertilization
accounts for inheritance patterns. Chromosomes undergo segregation and independent assortment during meiosis and thus account for Mendel’s laws.
Chromosome Theory of Inheritance
A pair of two nearly identical chromosomes,
each of which consists of two identical sister chromatids after chromosome duplication and carries possibly different versions of the same genes
Homologous Chromosome
autosomes, a chromosome not directly
involved in determining the sex of an organism
Autosomal Chromosomes
determine an organism’s sex (male versus female). In
mammals, males have one X chromosome and one Y
chromosome
Sex Chromosome
Having pairs of homologous chromosomes. somatic cells; 2n
Diploid
having a set of single chromosomes with only one chromosome of each pair of homologous chromosomes; gametes; 1n.
Haploid
it is the process of cell division that produces haploid gametes from diploid cells within the reproductive organs of a sexually reproducing organism
Meiosis
There are ____ nuclear and cytoplasmic
division(s) in meiosis
2
There are ______ duplication(s) of DNA with ________ nuclear division(s) in Meiosis
2, 1
Chromosomes duplicate, Homologous chromosomes separate, sister chromatids separate
Meiosis occurs in gametes
Prophase I, Metaphase I, Anaphase I, Telophase I and Cytokinesis
Meiosis I
Prophase II, Metaphase II, Anaphase II, Telophase II and Cytokinesis
Meiosis II
There are two possibilities that are equally likely, so the four possible types of gametes will be made in approximately equal numbers
Independent assortment
DNA duplication → nuclear division (mitosis) + cell division (cytokinesis) → offspring that are identical to parent
Asexual reproduction
Asexual reproduction occurs in which kingdoms?
Bacteria and Arhaea
DNA duplication → 2× nuclear divisions (meiosis) + cell divisions (cytokinesis) → fertilization → offspring that are not identical to parents
Sexual Reproduction
if parent is successful, offspring
maybe not so
▶ requires another organism of the
opposite sex
▶ slower than asexual reproduction
Disadvantages of Sexual Reproduction
sources of variation that are not
mutation
1. meiosis
2. fertilization
Advantages of Sexual Reproduction
Meiosis reduces the resulting gametes’ chromosome number by half from __________ to ___________
diploid to haploid
the joining of two haploid gametes, restores the
diploid condition.
fertilization
duplication or loss of entire chromosomes, changes in the number of complete sets of chromosomes that occur when pairs of homologous chromosomes or sister chromatids do not separate during meiosis
nondisjunction
zygotes missing any one copy of an autosome;
usually fail to develop to birth due to missing essential genes
autosomal monosomies
zygotes with an extra copy of an autosome;
usually fail to develop to birth; for some of the smaller chromosomes (13, 15, 18, 21, or 22); an excess in gene dose & offspring that survive for several weeks – many years
autosomal trisomies
born a girl but express developmental delays and reduced fertility
triplo-X
a type of Klinefelter Syndrome ; a boy with small testes, enlarged breasts, and reduced body hair. The extra X chromosome undergoes inactivation to compensate for the excess genetic dosage
XXY
Jacobs Syndrome often few noticeable phenotypic differences, boy with macroorchidism, tall, macrocephaly (abnormally
large head), & hypertelorism (increased distance between two body parts, typically the eyes); more likely than to be diagnosed with asthma, autism spectrum disorder, & seizures. Some are infertile
XYY
Turner Syndrome, girl with short stature, webbed skin in the neck region, hearing and cardiac impairments, and sterility
X0
extra copy of part of a chromosome
partial duplication
loss of several genes with a section of a chromosome
deletion
the detachment, 180° rotation, and reinsertion of part of a chromosome
inversion
a segment of a chromosome dissociates and
reattaches to a different, non-homologous chromosome
translocation
the exchange of chromosome segments between two non-homologous chromosomes such that there is no gain or loss of genetic information
reciprocal translocation
Homologous chromosomes pair up and exchange segments, pairs of homologous chromosomes line up, pairs of homologous chromosomes split up, Two haploid cells from, chromosomes are still doubled
Meiosis I description
The sister chromatids finally separate, four haploid daughter cells result, containing single chromosomes
Meiosis II description
Homologous (non-sister) chromatids exchange corresponding segments, remaining attached at the crossover points. Sister chromatids remain joined at their centromeres
Crossing over in meiosis I
Recombinant chromosomes combine genetics information originally derived from different parents
crossing over in meiosis II
an organism with alternate forms of a
gene will express the form that is dominant.
Law of Dominance
