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Exam 2 Genetics
Chapters 6-10
| Question | Answer |
|---|---|
| Visual representation of family tree with history of studied trait. | Pedigree |
| Oldest generation at the____; youngest generation at the _____. | Top; Bottom |
| Used for generations (I being the oldest). | Roman numerals |
| Numbered from _____ to _____ within a single generation | Left; Right |
| Trait seen in roughly equal amounts of males and females Seem to skip generations. (Affected individual can have unaffected parents). | Autosomal recessive traits |
| Equal frequency of males and females No skipping of generations All affected individuals have an affected parent (affected individuals tend to be heterozygous) | Autosomal dominant traits |
| Affected phenotype seen more commonly in males Tend to skip generations. Affected males do not pass trait to sons. If woman is affected, 100% of sons will be affected | X linked recessive |
| Do not skip generations Seen in both males and females but more in females. Females can get disease from either parent while males can only get from mother Affected female will have 100% sons affected. Affected male will have 100% daughters affected | X linked dominant |
| Only males affected Affected males will have 100% affected sons Do not skip generations | Y linked |
| Non-identical twins; fraternal 2 separate eggs fertilized 50% average relatedness; same as any sibling pair | Dizygotic |
| Identical One zygote that splits very early in embryonic development | Monozygotic |
| % of twin pairs that have the same trait Monozygotic twins are 100% genetically identical; dizygotic approx 50% Used to evaluate genetic vs environmental factors Genetic influenced traits will show higher concordance in monozygotic twins | Concordance studies |
| Examines effects of genes vs environment Adoption parents have 0% relatedness to adopted child, but share same environment Adoptees tend to resemble biological parents (obesity, alcoholism) | Adoption studies |
| bacteria acquired genetic information from dead strain which permanently changed bacteria | Transformation (Fred Griffith) |
| What are the reasons for seeing a genetic counselor? | Positive family history Advanced maternal age Abnormal prenatal test results Infertility Ethnic background |
| What are some prenatal testing | Ultrasound, Amniocentesis, Chorionic villi sampling (CVS), Fetal cell sorting, Pre-implantation |
| What is a Postnatal testing? | Newborn screening, Heterozygote/carrier testing, Pre-symptomatic testing, Chromosome analysis/cytogenetic testing. |
| What's an Ultrasound? | Can be performed as early as several weeks after fertilization Noninvasive Gives image of fetus Anatomical abnormalities, neural tube defects, nuchal translucency, amount of amniotic fluid, fetal size |
| What is a Amniocentesis? | Can be done 15-18 weeks Trans-abdominally or trans-vaginally Ultrasound guided Needle inserted and ~15ml of fluid extracted Fluid can be tested directly or fetal cells cultured prior to testing. Each ml of fluid contains only ~10-15 cells |
| What's a Chorionic villi sampling (CVS) | Ultrasound guided Small section of chorion is suctioned off (10-15mg) Large number of fetal cells reduces time/need for culturing Increased risk for limb reduction of performed at earlier gestation Eliminates proper blood supply to developing li |
| Isolation of fetal cells from maternal bloodstream Minimally invasive | Fetal cell sorting (in development) |
| IVF procedure One cell is removed from 8-16 cell embryo and tested Only “healthy” embryos are implanted | Pre-implantation |
| Positive family history or particular ethnic background Biochemical or molecular testing | Heterozygote/carrier testing |
| Inherited cancer alleles – increased risk for cancer Late-onset diseases (Huntington disease) | Pre-symptomatic testing |
| Diagnostic and prognostic value in cancer Infertility Child with structural chromosomal abnormality (Inherited or de novo mutation) | Chromosome analysis/cytogenetic testing |
| Diploid organisms have 2 alleles for each gene that Separate during meiosis – only one gamete enters each gamete | Principle of Segregation |
| DNA made up of 4 different nucleotides in equal amounts | Tetranucleotide theory |
| 2 alleles of a gene separate independently from alleles at other loci/other genes | Principle of Independent Assortment |
| Chromosomes follow independent assortment if…. | genes are on the same chromosome, they tend to travel together |
| close together on the same chromosome | Linked genes |
| If 2 genes are on the same chromosome, but far apart, crossing over can allow for recombination of gametes | crossing over |
| Genes very far apart on the same chromosome will always be separated by_____, and are not considered to be ___. | crossing over; linked |
| Horizontal lines indicate | Actual chromosome |
| individual heterozygous for 2 different genes where both dominant alleles are on __________, and both recessive alleles are on its _________. | One chromosome; homologous chromosome |
| For determination if two genes are linked and genotype is known. | Testcross |
| One individual heterozygous for both traits x individual homozygous recessive for both traits | Testcross setup for linkage |
| If not closely linked, alleles will assort ______. | independently |
| 2 alleles will always travel together, All offspring are non-recombinant | If closely linked |
| If closely linked, it can be separated by | crossing over |
| Small number of recombinant progeny/chromosomes is seen when | Crossing over |
| Single cross over produces 50% _______ and 50% | Nonrecombinant chromosomes; recombinant chromosomes |
| = number of recombinant progeny x 100 total number of progeny | Recombination frequency |
| Smaller the recombination frequency | More closely linked |
| Genes are linked | 50% |
| Genes are not linked | <50% |
| Both wildtype alleles are on one chromosome; both mutant alleles are on the homologous chromosome | Cis configuration/coupling |
| Each chromosome has one wildtype allele and one mutant allele | Trans configuration/repulsion |
| Coupling and Repulsion for ________ individuals | heterozygous |
| Between genes on different chromosomes Independent assortment/random segregation during Metaphase/Anaphase I Produces 50% recombinant/50% non-recombinant gametes | Interchromosomal |
| Between genes on same chromosome Crossing over during Prophase I Usually produces recombinant gametes less than 50% | Intrachromosomal |
| Relative position of different genes based on recombination rates Does NOT state actual chromosome, or position (locus) Distance measured in map units or centimorgans (cM) | Genetic mapping |
| Any genes with 50% recombination are either__________, or very far apart on the ________. (crossing over always separates them) | on different chromosomes; same chromosome |
| Locates gene to a specific chromosome/region of chromosome | Physical mapping |
| Chromosome deletion studies – how phenotype is affected/what genes may be missing | Deletion mapping |
| Fusion of 2 cell types (altered by viruses or tumor cells to allow cell lines – uninhibited growth) Most chromosomes are lost | Somatic cell hybridization |
| 2 distinct nuclei | Heterokaryon |
| Fluorescence In Situ Hybridization and DNA sequencing | Molecular Analysis |
| Yields base pair distance between two genes | DNA sequencing |
| Probe complementary to gene sequence will bind to DNA | Fluorescence In Situ Hybridization (FISH) |
| Example of deletion mapping | Duchenne m.s. -Some affected males have small deletions -X linked disease (common area for all of them) |
| Types of Bacteria | Prototrophic and Auxotrophic |
| Wild-type Can grow on minimal media Contains minimal nutrients – carbon, nitrogen, phosphorous, vitamins, ions | Prototrophic |
| Can not produce an essential enzyme or manufacture essential molecules Will only grow on media that contains the “missing” substance Complete media | Auxotrophic |
| Liquid media Bacteria dies off when nutrients are used up or waste buildup becomes toxic Bacteria grow singularly – no colonies | Suspension culture |
| Growth media in agar Isolate individual colonies Each colony originates from a single bacterium | Culturing bacteria on Petri dishes |
| Gives “carbon copies” of petri dish colonies Use sterilized velvet to make a stamp Some bacteria from each colony is transferred to velvet, and then transferred to new dishes | Replica plating |
| Most consist of a single, circular chromosome Very little “extra” DNA between genes Plasmids | Bacterial genome |
| A plasmid that can replicate independently AND also has the ability to incorporate into chromosomes | F factor episome |
| One bacteria directly transfers DNA to another bacterium Cytoplasmic connection forms, and either entire plasmid or part of the chromosome is transferred from donor to recipient Crossing over may occur between homolgous regions | Conjugation |
| Bacteria takes up DNA from surrounding environment Recombination may occur | Transformation |
| Viral particle introduced DNA from a bacterium into a new bacterium | Transduction |
| Fertility factor/F factor contains ori and genes needed for? | conjugation |
| Forms a sex pilus – extension of cell membrane __ factor separates, and one strand is transferred into ___ __ contains __ factor | F; F- F+; F |
| F+ cell that has F factor incorporated into chromosome | HFr bacteria |
| As F factor enters recipient, some chromsome enters – amount depends on time length of contact. Recipient is not usually converted to F+ since the F factor is nicked in the middle Crossing over can occur btw homologous regions. | Conjugation |
| F factor excises out of a chromosome in a Hfr cell F′ plasmid now contains F factor and some genes from chromosome Enters F- bacteria Produces merozygotes – partially diploid | F' Bacteria |
| Uptake of DNA and incorporation into chromosome or plasmid -Naturally occurring – dead bacteria -Artificially introduced Competent – cells able to take up DNA | Transformation |
| bacteria that have incorporated foreign DNA | Transformants |
| Many strains are avirulent Small and rapid reproduction Easy to culture Genome is single chromosome - haploid Wild-type are prototrophic | E. Coli has model organism |
| DNA or RNA (single or double stranded) as genetic material Can not reproduce on their own | Viral genetics |
| viral particles that infect bacteria | Bacteriophages |
| Virulent phages Viral DNA is injected into host cell where it replicated, transcribed, and translated into more phages Host cell bursts open to release viral particles Cannot undergo binary fission | Bacteriophage – lytic cycle |
| Temperate phages Phage DNA is incorporated into host genome – prophage Passed onto all progeny cells Can be transcribed and translated Can exit from host genome to enter lytic cycle | Bacteriophages – lysogenic cycle |
| Any gene is transferred | Generalized Transduction |
| Bacterial DNA is degraded Some may enter viral protein coat instead of viral genetic material Transducing phages Can become incorporated into new host’s genome | Transduction- Lytic cycle |
| Few genes are transferred/genes near certain sites of chromosome | Specialized Transduction |
| prophage enters at specific sites of host’s genome When prophage excises, it may do so imperfectly and bring some hot DNA with it Then introduced to new host | Transduction- Lysogenic cycle |
| Single strand directly codes for viral proteins | Positive strand RNA viruses |
| Must make complementary RNA strand, which then codes for proteins | Negative strand RNA viruses |
| Incorporate into host genome Must make DNA from RNA Reverse transcriptase Makes cDNA from DNA or RNA template Enters host genome as a provirus Can be transcribed and translated Some retroviruses contain oncogenes Cause tumors | Retroviruses |
| Three common genes | gag -Proteins that make up viral protein coat pol -Reverse transcriptase -Integrase – allows for insertion into host genome env -Glycoproteins on viral surface |
| Centromere is centrally located; arms equal length | Metacentric |
| Centromere is off center | Submetacentric |
| Centromere is close to one end p arm has satellites (knobs on stalks) | Acrocentric |
| Centromere is at one end Not present in humans | Telocentric |
| Complete set of chromosomes arranged in homologous pairs | Karyotype |
| Giemsa stain; most common Stains A-T rich regions | G banding |
| Stains centromeric heterochromatin and portions of chromosomes with large sections of heterochromatin | C banding |
| Stains G-C rich regions Gives opposite banding pattern of G banding | R banding |
| UV light is used Same pattern as G banding | Q banding |
| Types of chromosome mutations | Chromosomal rearrangement, Aneuploidy, Polyploidy |
| Structure is altered | Chromosomal rearrangement |
| Abnormal number of chromosomes Missing one or more/having one or more extra | Aneuploidy |
| 1 or more additional sets of chromosomes | Polyploidy |
| Chromosome rearrangements (4 types) | Duplications, Deletions, Inversions, Translocations |
| Section of chromosome is doubled | Duplications |
| repeated segment is right after the original | Tandem |
| repeated segment is located elsewhere on chromosome, or on a different chromosome | Displaced |
| Sequence is inverted from the original sequence | Reverse |
| During paring of homologous chromosomes, duplicated region loops out Offspring receive two copies of involved genes from parent with duplication, and a third copy of the other parent | Duplications (Heterozygotes) |
| loss of a portion of chromosome Large deletions can be seen cytogenetically; microdeletions by FISH If the deleted region includes the centromere, entire chromosome will be lost Usually lethal in homozygous form | Deletions |
| Normal chromosome must loop out during pairing Partial monosomy for all involved genes | Deletions (Heterozygous) |
| Affects gene dosage | Deletions - heterozygotes |
| Expression of mutant/recessive phenotype due to loss of normal/dominant copy | Pseudodominance |
| Both copies of the gene are needed to manufacture adequate amount of gene product (One gene doesn’t produce enough for a normal phenotype) | Haploinsufficiency |
| Two breaks in chromosome, then flipped and reinserted | Inversions |
| Both breaks occur in one arm | Paracentric inversion |
| Breaks on both arms; centromere is involved Can change morphology by altering centromere position | Pericentric inversion |
| Disruption of a gene – no functional product Position effect (Change in gene position can affect gene expression) | Inversions Effects |
| Chromosomes have to loop when pairing | Inversion loops |
| If crossing over occurs within loop: Creates a dicentric chromosome and an acentric chromosome -Acentric is lost -Dicentric forms a dicentric bridge, and breaks -Nonviable recombinant gametes | Paracentric inversion loops |
| Crossing over within loop creates recombinant chromosomes with duplications and deletions (nonviable) | Pericentric inversion loops |
| Rearranges genetic material to another part of the same chromosome; or nonhomologous chromosome | Translocations |
| Segment moves from one chromosome to another | Nonreciprocal Translocations |
| Exchange between two chromosomes | Reciprocal Translocations |
| Loss of gene function – break Position effect Creation of a fusion/abnormal protein | Translocations Effects |
| Between two acrocentric chromosomes (13, 14, 15, 21, 22) 2 q arms are joined at a common centromere (Forms a metacentric chromosome if two chromosomes are same size) Small fragment is usually lost (acentric) | Robertsonian translocation |
| Named after the chromosome that is the origin of the centromere | Translocated chromosome |
| Have one normal copy of a chromosome, and one translocated one -During meiosis, all 4 chromosomes will associate -Can segregate 1 of 3 ways | Translocated chromosome (Heterozygotes) |
| Both normals go to one pole; both translocated go to the other (balanced) | Translocation segregation (Alternate) |
| Each pole gets one normal, and the opposite translocated Partial monosomies/partial trisomie (unbalanced) | Translocation segregation (Adjacent 1) |
| Each pole gets both the normal and translocated of the same chromosome (Inviable; rare) | Translocation segregation (Adjacent 2) |
| -Under certain conditions/culturing techniques, chromosomes develop breaks/restrictions at particular locations -Now routinely tested for by FISH analysis | Fragile sites |
| Abnormal number of chromosomes Caused by: -Loss of chromosome during cell division; random error or loss of centromere; nondisjunction -Robertsonian translocation | Aneuploidy |
| -Nullisomy 2n – 2 – missing both members of a homologous pair -Monosomy 2n – 1 – missing one chromosome -Trisomy 2n + 1 – one extra chromosome -Tetrasomy – 2n + 2 – two extra chromosomes of the same type/homologous | Types of Aneuploidy |
| -Often lethal if constitutional Can see elaborate abnormalities in tumor cells -X inactivation in mammals takes care of extra Xs, so not as severe | Aneuploidy |
| -Primary 3 free copies of #21 -Familial Extra copy due to translocation | Down Syndrome (Aneuploidy) |
| Both chromosomes of a homologous pair from the same parent Probably originated from a trisomy (1 chromosome is lost early in development) Recessive diseases (One carrier parent and one normal parent can have an affected child) | Uniparental Disomy |
| Nondisjunction in later development can cause “patchiness” – normal cells and abnormal cells Approximately 50% of Turner syndrome can be mosaics 45, XO/46, XX | Mosaicism |
| Extra sets of chromosomes -Triploid – 3n; tetraploid – 4n Common in plants – more tolerant of extra sets of chromosomes | Polyploidy |
| Extra set is from same species (attacking self) -Error in cell division Extra chromosome caused pairing problems; especially with odd numbers -3n usually sterile; produce small seeds | Autoploidy |
| Hybridization between two species AABBCC x GGHHII F1 generation ABCGHI – not homologous -Gametes are inviable, but may be able to reproduce asexually Nondisjunction error can lead 2x, which could then reproduce sexually | Allopolyploidy |
| DNA made up of 4 different nucleotides in equal amounts. DNA doesn’t have the variety needed for genetic material | Tetranucleotide theory |
| Consisted of DNA and protein | Nucleic acid |
| Protein is composed of __ different amino acids | 20 |
| A=T and G=C | Chargaff's rule |
| What is the chemical nature of the transforming substance? | DNA because only DNase destroyed transforming substance |
| Which part of the phage-its DNA or its protein-serves as the genetic material and is transmitted to phage progeny? | DNA, not protein, is the genetic material in bacteriophages |
| Diffraction pattern | Gives information on molecular structure |
| WHat substance-RNA or protein- carries the genetic material in viruses? | RNA |
| Carbon in sugar can be referred to as | # prime |
| Ribose | RNA -OH at 2'carbon (less stable) |
| Deoxyribose | DNA (removing an oxygen) -H at 2' carbon |
| Phosphorous and 4 oxygen Negatively charged Attached to 5′ carbon | Phosphate group |
| Nitrogenous base | Covalently bonded to 1′ carbon |
| two main types of Nitrogenous base | Purine and Pyridine |
| Purine | Double-ringed; six- and five-sided rings |
| Two types of Purine | Adenine Guanine |
| Two types of Pyridine | Cytosine Thymine (DNA only) Uracil (RNA only) |
| Single-ringed; six-sided ring | Pyridine |
| RNA only | Uracil and ribose |
| DNA only | thymine and deoxyribose |
| Nucleoside | base and sugar |
| Nucleotide | Nucleoside + phosphate |
| DNTP | Deoxy-nucleoside-tripphosphate |
| Nucleotides covalently bonded? | phosphodiester bonds |
| Phosphate group of one nucleotide bound to ….. | 3'C of previous sugar |
| Backbone consists of….. | alternating phosphates and sugars |
| DNA double helix (antiparallel) | 2 antiparallel strands with bases in interior Bases held together by hydrogen bonds |
| Backbone? | Always has one 5′ end (phosphate) and one 3′ end (sugar –OH) |
| complementary strands | Complementary base pairing?? |
| Base pairing | 2 between A and T (easy to pair); 3 between G and C |
| B-DNA (most common) | Shape when plenty of water is present Right hand/clockwise turn; approx 10 bases per turn |
| A-DNA | Form when less water is present; no proof of existence under physiological conditions Shorter and wider than B form Right hand/clockwise turn; approx 11 bases per turn |
| Z-DNA | Left hand/counterclockwise turn Approx 12 bases per turn (narrower) Found in portions with specific base pair sequences (alternating G and C |
| Central dogma | Replication, Transcription and translation |
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