Download Honors Genetics: MIDTERM Exam Review REVIEW ALL OLD

Honors Genetics: MIDTERM Exam Review
REVIEW ALL OLD QUIZZES/TESTS!
Chapter 1: Introduction to Genetics
Know the differences between PROKARYOTES and EUKARYOTES
PROKARYOTES lack a nucleus and membrane-bound organelles. DNA is found as a circular PLASMID.
EUKARYOTES contain a nucleus and membrane-bound organelles. DNA is found in nucleus as chromatin and
chromosomes.
What is the function of DNA? Carries information for structure and function of living things; Information contained
produces proteins.
What is a MUTATION? Change in genetic information.
What causes mutations? Variety of factors: environment, personal choices, genetics, radiation, chemicals
What 3 categories do mutations fall into and provide an example of each.
ADVANTAGOUS: Natural selection
INCONSEQUENTIAL: Doesn’t make a difference.
DILATERIOUS: Harmful
What is RECOMBINATION? Combining DNA from different organisms into a single genome.
Describe CLONING. Taking SOMATIC DNA from one organism and placing into the EGG of another organism to produce
and embryonic CLONE of the original organism.
What organisms are currently being genetically engineered and for what purposes?
Plants, animals, and bacteria. Plants that have natural immunity to pests and weeds. Bacteria that produce human
chemicals and hormones. Animals that have more meat/milk.
Know the following terms
DIPLOID: Full genetic information. Located in somatic/Body cells
HAPLOID: Half genetic information. Located in gametes/sex cells
HOMOLOGOUS CHROMOSOMES: Chromosomes are the same size, centromeres are in the same location,
contain same genetic information.
ALLELE: Variation of a gene; possibilities
GENOTYPE: What is “written” on the chromosomes. (TT, Tt, tt)
PHENOTYPE: What is expressed or what you see. The physical expression of a gene. (tall, short)
Chapter 2: Mitosis and Meiosis
Know the following terms:
CHROMATIN: UNCOILED DNA; present when the cell isn’t dividing.
CHROMOSOMES: COILED DNA; present when the cell is performing mitosis.
SISTER CHROMATIDS: joined together by centromere; matching alleles at same place
HOMOLOGOUS CHROMOSOMES: See Above
Know the ORGANELLE chart from your notes to describe the function of cell organelles
Describe the appearance of chromosomes based on centromere location.
Chromatin is DNA during interphase, when the cell is not dividing. It is coiled like spaghetti on a plate, not condense to
form chromosomes (X). The centromere holds sister chromatids together and the location of the centromere is used to
assist in identification of chromosome # during karyotyping of an individual. METACENTRIC: centromere in center
SUBMETACENTRIC: centromere JUST ABOVE metacentric
ACROCENTROC: centromere JUST ABOVE metacentric
TELOCENTRIC: centromere at END of sister chromatids
Describe the cell clock and apply to the type of cell that divides
G1 and G2 are for growth and work
S is for replication of DNA
M is for Mitosis/Meiosis and Cytokinesis
LABILE cells are constantly dividing and do not exit the cell
cycle.
STABILE cells are in the cell cycle during growth and repair
but will QUIESCE and simply work.
PERMANENT cells are made during embryonic
development and will simply work for the remainder of
the life span, never to divide again.
What is the purpose of MITOSIS?
Diploid to Diploid division of the nucleus for the production of somatic/body cells during growth and repair.
What is the order of steps? PROPHASE, METAPHASE, ANAPHASE, TELOPHASE
What is the general description of chromosome action in mitosis? DNA coils, matched/lines up along metaphase plate,
centromere splits, separating chromosomes so they can travel to opposite ends of the cell to be segregated into 2 new
nuclei.
What is the purpose of MEIOSIS?
Diploid to Haploid division of the nucleus for the production of germline/gametic cells for the purpose of reproduction.
What is the order of steps? Occurs in 2 phases, order of steps is the same as in Mitosis.
Know the following terms:
MONAD: single chromosome with centromere (chromatid)
DYAD: double chromosomes held with centromere (sister chromatids)
TETRAD: paired chromosomes (homologous chromosomes)
GENETIC VARIATION: created through meiosis allows for “shuffling” of genetic information.
CROSSING OVER: occurs at the end of the prophase 1 that allows for transfer of genetic information of maternal and
paternal DNA during meiosis.
Know the similarities and differences between SPERMATOGENESIS and OOGENSIS.
Spermatogenesis begins during puberty and will last the remainder of life. It produces 4 genetically different haploid
cells.
Oogenesis begins during fetal development, stops and begins again at puberty, stops and begins again at ovulation and
fertilization. It produces 1 mature ova and 3 polar bodies
Chapter 3: Mendelian Inheritance
Be able to analyze an AUTOSOMAL DOMINANT and AUTOSOMAL RECESSIVE pedigree.
Be able to select INDEPENDENTLY ASSORTED alleles for DIHYBRID and TRIHYBRID crosses, selecting answers from a multiple
choice list.
Know your VOCABULARY!
characteristic/trait: the inherited characteristic that is being studied.
unit factors/alleles: options that can be passed from parent to offspring.
gene segregation: during meiosis, the separation of alleles into egg and sperm
phenotype: the physical expression of a gene.
genotype: what is occurring in the genetic code, HH, Hh, hh
homozygous: inheriting the SAME allele from each parent; HH, hh
heterozygous: inheriting different alleles from each parent; Hh
Know Mendel’s Postulates
Unit factors occur in pairs: 2 copies of each gene; 2 copies of each chromosome.
Dominant/Recessive: when the dominant trait is present, it is expressed over the recessive trait. Recessive is
only expressed in the homozygous form.
Segregation: alleles will separate during meiosis into egg/sperm.
Independent Assortment – for more than 2 traits: alleles will separate independently during meiosis, greatly
increasing genetic variation.
Chapter 4: Modification of Mendelian Ratios
The allele that occurs most frequently in a population WILD-TYPE ALLELE
The range of expression of a mutant genotype EXPRESSIVITY
Allele that results in complete loss of function NULL ALLELE
The percentage of individuals that show some degree of expression of a mutant genotype PENETRANCE
Expression of one gene or gene pair modifies the expression of another gene EPISTASIS
The joint expression of BOTH alleles in a heterozygote CODOMINANCE
A condition of males since they do not carry 2 homozygous sex chromosomes HEMIZYGOUS
A mutation that results in the death of the organism, usually before they can reproduce LETHAL ALLELE
Expression of genes is influenced by the sex hormone concentration of the individual SEX-INFLUENCED INHERITANCE
Know how to differentiate between different pedigrees
Autosomal Dominant/Autosomal Recessive
X-linked Dominant/X-linked Recessive
Review blood group inheritance
ABO: Codominance; A and B are codominant, O is recessive
MN: M and N are codominant
Rh Factor: Rh+ is dominant, Rh- is recessive
Describe the issues surrounding sex-linked inheritance in human males
Males are HEMIZYGOUS at the 23rd chromosome, inheriting only a single X chromosome from the mother. This
impacts males in the sense that X-linked disorders will impact the male offspring more frequently than female offspring.
heteromorphic chromosomes: sex chromosomes that are different; XY
homomorphic chromosomes: sex chromosomes that are the same; XX
Primary sex differentiation: gonad development for production of gametes
Secondary sex differentiation: other characteristics of overall appearance; mammary glands, facial hair, etc.
Unisexual: “one sex”; organisms are either male or female
bisexual/hermaphroditic: “two sexes”; containing both male and female sex characteristics
intersex: between two sexes; neither fully male or female
heterogametic sex: gametes look different from one another; males produce an X and Y chromosome
homogametic sex: gametes look the same; females produce 2 X chromosomes
Bipotential gonads: gonadal ridges can become ovaries or testes
Mullerian ducts: become fallopian tubes and uterus of the female reproductive system
Wolffian ducts: become vas deferens, glands of male reproductive system
disjunction vs nondisjunction: disjunction is the NORMAL separation of tetrad – dyad – monad. Nondisjunction is the
abnormal condition of tetrads not separating or dyad centromeres not splitting that causes chromosomal aberrations to
occur during meiosis.
What is the purpose of MEIOSIS? Division of nucleus to segregate DNA into new gametes. DIPLOID to HAPLOID.
Reductional division and Equational division of centromeres that allow for separation of chromosomes to achieve a
haploid condition.
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What is the order of steps? Occurs in 2 phases, order of steps is the same as in Mitosis. Prophase 1 is the most
significant as CROSSING OVER occurs that allows for genetic variation.
What is the general description of chromosome action in meiosis? Beginning of Meiosis 1 begins with a TETRAD;
at the end of Meiosis 1, there is a DYAD in each cell produced; at the end of Meiosis 2, there is a single MONAD
in each cell produced.
How is meiosis different in human males and human females? Meiosis in males in a CONTINUOUS process,
beginning at puberty. Meiosis in females is a HALTING process. It begins during the 12 th week of fetal
development, arresting at Prophase 1 and not beginning again until puberty begins. Then, each month a single
immature ova completes Meiosis 1 prior to ovulation and will complete Meiosis 2 following fertilization by a
mature sperm.
What are the specific steps of Prophase 1? What is significant about Prophase 1?
o Leptonema: chromatin condenses to form chromosomes
o Zygonema: rough pairing of homologs
o Pachynema: synapsis; formation of tetrads
o Diplonema: crossing over at chaisma
o Diakinesis: preparing for prometaphase1
Describe oogenesis and spermatogenesis in humans. How are they alike? How are they different?
Spermatogenesis produces 4 mature spermatozoa that are capable of fertilizing an egg. In humans, the sperm SHOULD
contain 23 single chromosomes = the haploid number.
Oogenesis produces 1 mature ova and 4 polar bodies. Only the ova is capable of sustaining fertilization due to the
presence of organelles and cytoplasm that will permit embryonic development until the placenta and amniotic sac are
formed later in gestation. The ova SHOULD also contain the human haploid number of 23.
Understand the process of sex differentiation/fetal development in humans (p. 99)
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Gonadal ridges are produced during the 5th week of gestation. The embryo is potentially bipotential at this
stage the gonads can become ovary or testis.
Cortex portion can develop into ovarian tissue; Mullerian ducts will become fallopian tubes and uterus.
Medulla portion can develop into testis; Wolffian ducts will become vas deferens, ejaculatory duct, and male
glands.
Presence or absence of the Y chromosome determines the transition of gonadal ridges into ovaries or testes.
In the absence or malformation of genetic information of Y chromosome, no male GONADAL development
occurs.
During the 12th week of fetal development, ovaries begin meiosis for the production of eggs.
Describe nondisjunction and the impact it CAN have on gamete chromosome numbers.
Nondisjunction is the abnormal condition of tetrads not separating or dyad centromeres not splitting that causes
chromosomal aberrations to occur during meiosis. SEE DIAGRAM from CHAPTER 5 QUIZ!
Be able to differentiate human chromosome numbers (karyotypes) in –somic conditions.
Be able to identify the critical areas AND describe the functions of the Y chromosome and its influence in sex
differentiation. SEE CHAPTER 5 QUIZ!!
What term is used to describe the relationship between the X and Y chromosomes? HETEROMORPHIC
Describe the genotype and phenotype – Be able to ID the karyotype - of the following -somic conditions:
Turner Syndrome
Klinefelter Syndrome
Down Syndrome
45, X
Patau Syndrome
47, 13+
47, XXY
Edward Syndrome
47, 18+
KNOW Down Syndrome! Cause, description, statistics, pre-natal diagnosis (p.115)
47, 21+