Flashcards in Genetics Deck (59):
Repeating sequence of events in the life cycle of a dividing cell.
What are the four stages of the cell cycle?
G1: growth and metabolism.
S: synthesis of DNA.
G2: growth and metabolism.
What are the three stages of interphase?
G1, S, G2.
What is the major difference between cells in G1 vs G2?
Cells in the G2 stage have twice as much genetic material (DNA) as those in G1.
What is Mitosis?
Nuclear division usually followed by cytoplasmic division that forms two genetically identical daughter cells.
What are the four phases of mitosis?
What is prophase?
Chromatin condenses into distinct chromosomes. The nuclear membrane disintegrates, and spindles form at opposite ends of the cell.
What is Metaphase?
Chromosomes align on a plane that is equally distant from both spindles.
What is anaphase?
The paired chromosomes move to opposite ends of the cell.
What is telophase?
Chromosomes are grouped in separate new nuclei in the emerging daughter cells. At the end of mitosis, two cells with identical genetic material have been produced.
What is a gene?
Section of DNA that codes for a specific protein.
Genes are arrange lengthwise on the chromosome
What are homologous chromosomes?
Chromosomes that occur in pairs; they are the same length and have alleles for the same traits at corresponding locations.
What does Haploid mean?
A cell that contains only one chromosome from each homologous pair.
What is diploid?
A cell that contains a pair of each homologous chromosome; on set is inherited from each parent.
Examples: body cell, fertised egg
What is a primary sex cell?
A cell contained in the gonads that will eventually become a gamete.
What is meiosis?
Cell division that produces haploid gametes from diploid cells. Usually four gametes are formed from one diploid cell.
Contrast spermatogenesis with oogenesis.
Spermatogenesis: the production of sperm cells.
Oogenesis: the production of egg cells. usually only one egg is formed from one diploid cell.
What is a polar body?
Small, non-functioning cell produced as a result of oogenesis (egg formation)
Summarize the work of Gregor Mendel?
A 19th century monk who studied heredity in garden pea plants, he published the first genetic studies and was known as the "father of genetics".
What is Mendel's Law of Dominance?
When orgaanisms that are pure breeds for contrasting traits are crossed, the trait expressed by the offspring is the dominant trait.
What is menel's Law of Segregation?
Modern form: during meisosis, homologous chromosomes (with the alleles they carry) separate and go to different gamete cells.
What are Alleles?
One of two or more different forms of a gene?
What does homozygous meant?
Having two identical alleles for a trait.
Examples BB, bb
What does heterozygous?
having two different alleles for a trait.
What does Genotype mean?
The genetic make-up of an organism; the actual genes an organism has for a trait.
Example: a cat with a brown-eyed phenotype may have a heterozygous genotype (one allele for brown, one allele for blue.
What is a phenotype?
The expression of a genotype; can be an appearance or a function of an organism.
Examples: tall, blue eyes, type B blood.
What is Mendel's Law of Independent Assortment?
Modern Form: the inheritance of alleles on one homologous chromosome pair has no effect on the inheritance of alleles on a different homologous chromosome pair.
Summarise the work of Thomas Hunt Morgan?
received the Nobel Prize for research on a fruit fly. He located certain genes on the chromosomes; discovered X-linked genes.
What does linkage mean?
Genes that are inherited together because they are located on the same chromosome; they do not independently.
What does Crossing Over mean?
During meiosis, homologous, chromosomes exchange genes, results in genetic recombination.
What does mutation mean?
The chemical change of a gene (DNA) that may change or prevent its function.
What are some dominant human traits?
Normal color vision.
What are some recessive human traits?
Color- blind vision.
What are sex chromosomes?
The pair of chromosomes that determines the sex of an individual. In humans: males - XY; females - XX
Sex-Linked Traits (X - linked traits)
Traits that are carried on the sex chromosomes?
Examples: color-blindness, hemophilia.
What are some diseases caused by gene mutations?
What are Chromosomal Aberrations?
When the number of chromosomes is abnormal. May result in Down syndrom, Trisony 21 or Klinefelter's syndrom - XXY
What does Trisomy mean?
When the genotype contains three copies of a chromosome.
Example: trisomy 21 - Down syndrome
What is Nondisjunction?
The failure of homologous chromosomes to separate in meiosis; can result in gametes with an abnormal number of chromosomes.
Name three disorders resulting from nondisjuntion.
What is translocation?
The relocation of a chromosome or piece of a chromosome to another chromosome; may cause a genetic disorder.
What are the characteristics of Klinefelter's syndrome?
Male with XXY genotype.
may have learning difficulties.
What are the characteristics of Turner's syndrome?
Female with XO genotype (missing second X)
short, webbed neck
underdeveloped sexually; sterile.
poor spatial-relation skills.
What is a Barr body?
A darkly staining mass that appears in the nucleus of female cells; it is an x-chromosome that has been inactivated.
What is sickle-cell anemia?
Genetic disorder caused by a point mutation of DNA, resulting in a single amino acid substitution.
Red blood cells become sickled because of abnormal hemoglobin.
Common genetic disorder of African Americans and Hispanics.
What does Co-dominance mean?
When both alleles of a heterzygous genotype are expressed (neither is recessive)
What does pedigree mean?
A chart that shows the genetic family history of a specific trait.
What is the probability that a couple will have three girls in a row?
1/2 x 1/2 x 1/2 = 1/8
a 50% chance for each separate event.
What is the probability that a couple will have five daughter and a son next?
1/2; Each birth is an independent event. Probability for a single event does not remember past events.
What is Recombinant DNA?
Molecules that contain DNA from different sources; used in genetic engineering.
What are plasmids?
Small circular DNA in bacteria and some eukaryotes, that carries genes separate from the main chromosome, including those for antibiotic resistance in bacteria.
What are Restriction Enzymes?
Enzymes that act as "biochemical scissors" by cutting DNA in specific places; used in genetic Engineering.
What is the Watson-Crick DNA Model?
-two chains of nucleotides running in opposite directions.
-chains are connected by bonds between sugars and phosphates.
- between chains, nitrogen bases are connected by weak hydrogen bonds.
What are the three types of RNA?
- transfer RNA
- ribosomal RNA
What is Protein Synthesis?
Assembly-line-like process of joining amino acids to form polypeptides; takes place at the ribosomes.
What is the genetic code?
The sequence of nucleotides in a DNA molecule that determines the proper formation of protein. Each three-letter codon specifies an amino acid or a stop signal.
What is the Gene Pool?
The total of all the genes in a population at a certain time.
What is the Hardy-Weinberg Principle?
Allele frequencies and genotype frequencies remain constant through time, providing that the population is large, random matings occur, there is no natural selection, and no new mutations or migration.