exam 3 Flashcards
What are chromosomes?
Cellular structure consisting of one DNA molecular and associated proteins
What is a haploid cell?
A cell containing only 1 set of chromosomes
1n
What is a diploid cell?
A cell containing of two sets of chromosomes (one set from each parent)
2n
What is the cell cycle?
An ordered sequence of events in life of a cell.
- Gap 1 (g1)- primary growth phase of cell
- Synthesis (s)- DNA replication
- Gap 2 (g2)- second growth phase, preparation for separation of genome
- Mitosis- separation of two genomes
- Cytokinesis- separation of cytoplasm
what are duplicated chromosomes?
sister chromatids that are held together by cohesion
what is the centromere?
region on each sister chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences
What is mitosis?
the separation of daughter genomes. Start with 1 cell and end with 2 identical cells. 5 phases: Prophase Prometaphase Metaphase Anaphase Telophase
what is prophase?
chromosomes condense, sister chromatids visible on each chromosome, nuclear envelope breaks down, spindle forms
what is prometaphase?
microtubles attach to kinetochores on chromosomes, chromosomes begin moving to center of cell
what is metaphase?
chromosomes line up at plate, chromosomes are arranged so that the sister chromatids face opposite poles
what is anaphase?
cohesion is degraded between sister chromatids, they are separate now and called daughter chromsomes, pulled to opposite poles.
what is telophase?
nuclear envelope reforms
what is cytokinesis?
separation of cytoplasm, occurs after mitosis, happens between animals and plants.
describe how cytokinesis happens in plants and animals.
in animals, it involves a cleavage furrow.
in plants, it involves a cell plate
What is binary fisson in bacteria?
reproduction is clonal, single circular bacterial chromosomes are replicated
how is the cell cycle regulated?
molecular signals within cytoplasm are responsible for regulating cell cycle, positive regulators.
What are the cell cycle check points?
G1/S: does cell divide? Influenced by external signals and DNA damage, some cells enter GO phase.
G2/M: was DNA replication successful? DNA damage, inaccurate replication.
Spindle: are all chromosomes attached to spindle? Prevent incorrect separtion of chromosomes
Define cancer.
unrestrained growth of cells resulting in a clump of cells called a tumor. A failure of cell cycle control.
A benign tumor: cells remain at original site, often described as noncancerous
A Malignant tumor: cells have genetic and cellular changed that enable them to spread to new tissues
Metastasis: spread of cancer cells to locations distant from their original site
What is Proto-oncogene?
a normal non-mutated gene that has potential to become an oncogene (causes cells to become cancerous)
what is a tumor-supressor gene, and P53 protein?
tumor suppressor gene prevents the development of mutated cells.
P53 detects DNA damage and halts cell division until DNA is repaired- if DNA cant be repaired it stimulates apoptosis of cell (programmed cell death)
What is inheritance?
traits are transmitted directly from parents to offspring.
What is the blending theory of inheritance?
paradox: if blending occurs, why dont we all look the same?
What is sexual reproduction?
two parents give rise to pffspring that have unique combinations of genes inherited from the parents.
what is asexual reproduction?
a single individual is the sole parents and passes coopies of all its genes to its offspring (ex: bacteria, some plants)
what is meiosis?
one DNA replication, two rounds of division:
Meiosis 1- reproduction division, each daughter cell contains one homologue from each chromosome pair. Starts with 1 diploid cell, ends with 2 haploid cells, crossing over occurs.
Meiosis II- separates the sister chromatids for each homologue (1 cell —— 4 cells)
Prophase 1?
Chromosomes condense homologous chromosomes synapse, crossing over occurs
Metaphase 1?
pairs of homologous chromosomes line up at metaphase plate, homologous chromosomes line up facing opposite poles
anaphase 1?
homologous chromosomes are pulled apart, sister chromatids do not separate and migrate together, not identical because crossing over
telophase 1?
nuclear envelope reforms, resulting 2 cells are haploid
Meiosis II is similar to Mitosis because?
- Spindles migrate
- Microtubules attach to chromosome
- Chromosomes align
- Sister chromatids separate
- End result is 4 haploid cells
Mitosis VS Meiosis?
Mitosis: 1 Replication 1 Cell division no crossing over 2 cells made cells are identical Meiosis: 1 replicate 2 cell divisions Crossing over 4 cells made cells not identical
Who is Gregor Mendel?
Austrian monk who studied inheritance of pea plants
what is the true breeding strain?
strain that produces only the same trait as parent over many generations of self-polination.
F1 generation/
first generation. Mendel allowed the F1 hybrids to either self pollinate or cross pollinate with other F1 hybrids. the result: saw white flowers among progeny (the F2 generation)
what is the dominant and reccessive trait?
dominant trait expressed in the F1 plants (or purple), Reccessive is the alternative trait not expressed in F1 plants but in the F2
What is the Law of Segregation?
two alleles for a heritable character segregation during gamete formation and end up in different gametes
what is a gene?
a discrete unit of hereidtary information
what is an allele?
alternative versions of a gene
what is a genotype?
genetic makeup or set of alleles of an organism
what is a phenotype?
observable physical and physiological traits of an organism
what is a dominant allele?
fully expressed in heterozygote (the capital letter)
what is a recessive allele?
phenotype is not observed in heterozygote (lower case)
what is homozygous?
a diploid cell having two identical alleles for a given gene (ex: PP, pp)
what is heterzygous?
a diploid cell having two different versions of a gene (ex: Pp)
what is the punnet square?
symbolic analysis of genotypes of all possible zygotes in a cross
what is test cross?
crossing an organism of unknown genotype with a recessive homozygote
what is the dihybrid cross?
examines 2 separate trains in a single organism
the rule of multiplication?
hint: AND. when crossing Pp X Pp, the probablility of proudcing pp pffspring is: from father: 1/2 from mother: 1/2 from pp: 1.4
addition rule?
probability of 2 mutually exclusive events occurring simultaneously is the sum of their individual probabilities
Hint: OR
what is the extensions to Mendel?
Mendel’s model of inheritance assumes that:
- each trait is controlled by a single gene
- Each gene has only two alleles
- there is a clear dominant-reccessive relationship between alleles
what is polygenic inheritance?
occurs when multiple genes are involved in controlling the phenotype of a trait
what is pleiotropy?
refers to an allele which has more than one effect on the phenotype. Pleiotropy affects are difficult to predict, because a gene that affects one trait often performs other unknown functions. EX: cystic fibrosis or sickle cell anemia
what is multiple alleles?
may be more than 2 alleles for a gene
ex: ABO blood type (3 alleles)
each individual can only have 2 alleles
what is codominance?
heterozygote show some aspect of both homozygotes
what is incomplete dominance?
heterzygote is intermedate in phenotype between the 2 homozygotes
sex chromosomes.
XX - female
XY - male
X chromosomes contain about 1,100 genes
Y chromosomes contain about 78 genes that code for about 25 proteins
what is epigenetics?
the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself
what is genetic screening?
the sequencing of human DNA in order to discover genetic differences, anomalies, or mutation that may prove pathological
