bio exam 3 review

asexual reproduction

one parent, clones, no genetic variation except mutations

sexual reproduction

two parents, meiosis + fertilization, produces genetically diverse offspring

why does sexual reproduction help evolution?

• increases genetic variation (crossing over, independent assortment)

• enhances ability to adapt to environmental changes

how many chromosomes are in human diploids?

2n= 46 

how many homologous pairs are in a chromosome?

23 pairs

how many autosomes are there?

22 pairs

what are the sex chromosomes?

1 pair; XX (female), XY (male)

shared homologous chromosomes:

• same size

• shape

• genes

• loci

not shared homologous chromosomes: 

• different alleles of those genes 

gene

DNA sequence coding for a trait

locus

gene’s location on a chromosome

allele

variant form of a gene

homologous pair 

maternal + paternal chromosome with same genes 

diploid (2n)

two sets of chromosomes

haploid (n)

one set (gametes)

karyotype

chromosomal portrait

autosomes

non-sex chromosomes 

sex chromosomes

X and Y

what is the human life cycle?

• adults (2n)

• meiosis

• gametes (n)

• fertilization

• zygote (2n)

• mitosis

• adult
  

what is the flowering plant life cycle?

• sporophyte (2n)

• meiosis

• spores (n)

• gametophyte (n)

• gametes

• fertilization

• zygote (2n)

how many divisions of meiosis are there and what are their functions?

two; Meiosis I (separates homologous chromosomes), and Meiosis II (separates sister chromatids)

how is meiosis different than mitosis?

meiosis involves two rounds of cell division, resulting in 4 haploid cells; mitosis undergoes only one round of cell division resulting in two diploid cells

animals- gametes formed directly: T or F?

True 

what are flowering plants?

spores from gametophytes, which produce gametes

what is crossing over?

exchange between homologs, recombinant chromosomes

what is independent assortment?

random chromosome alignment, gamete diversity

what does monozygotic mean?

one zygote, genetically identical; embryo splits 

what does dizygotic mean?

two eggs + two sperm; genetically siblings

what is nondisjunction?

the improper separation of chromosomes

what is primary nondisjunction?

meiosis I, all gametes abnormal

what is secondary nondisjunction?

meiosis II, half abnormal, half normal

what causes down syndrome?

trisomy 21

what causes klinefelter?

XXY

what causes turner syndrom?

X0

deletion

loss of a segment

duplication

repeated segment

translocation

segment attaches to another chromosome

what did Mendel contribute to the study of patterns of inheritance?

discovered basic inheritance laws using pea plants and controlled crosses

pure-breeding

always produces the same trait

hybrid

offspring of genetically different parents 

dominant

expressed with one allele

recessive

expressed with two alleles

phenotype

physical traits

genotype 

genetic makeup

homozygous

same alleles

heterozygous

different alleles

monohybrid cross

one gene

how do you predict offspring ratios?

use a punnett square or product rule for independent events 

what do you use to derive gametes?

independent assortment

incomplete dominance

heterozygote= intermediate phenotype

codominance

both alleles expressed (e.g., AB blood type)

multiple alleles 

more than 2 alleles form 

pleiotropy

one gene affects many traits

polygenic inheritance

traits controlled by many genes

environmentally influenced

phenotype affected by the environment

epistasis

one gene masks/modifies expression of another 

X-linked traits

passed from mother; more common in males

Y-linked traits

father —> son only

mosaic expression

one X in females becomes Barr body

what are pedigrees used for?

to track inheritance patterns across generations

what is DNA technology?

using DNA manipulation for research, medicine, agriculture, and forensics

transgenic organism

organism with DNA from another species 

plasmids

DNA vectors for gene insertion

restriction enzyme

cut DNA at a specific sequence

how do you express eukaryotic genes in bacteria?

insert gene into plasmid —> transform bacteria —> transcription and translation

short tandem repeats (STRs) 

repeated sequences used in DNA profiling

embryonic stem cells are…

pluripotent

adult stem cells are…

multipotent- able to produce several different effects on a gene

totipotent

can form all cell types + placenta

pluripotent 

can form nearly all body cells 

how do you clone an animal?

transfer nucleus from somatic cell into enucleated egg —> embryo —> surrogate

DNA probes

labeled DNA used to detect complementary sequences

PGD (preimplantation genetic diagnosis)

testing embryos for genetic disorders before implantation

basic features of viruses:

• noncellular

• genetic material + protein coat 

• require host to reproduce 

correct order of sizes of eukaryotic cells, protozoans, a virus, and bacteria:

virus < bacteria < eukaryotic cells < protozoans

classification features:

• genome type (RNA/DNA)

• shape

• envelope presence

• capsid symmetry

host range

virus infects only certain species/tissues due to receptor specificity 

replication cycle of the dsDNA virus:

attachment —> entry —> gene expression (synthesis) —> assembly —> release

replication cycle for HIV:

entry —> reverse transcription —> integration (provirus) —> replication —> budding

provirus

viral DNA integrated into host genome

what can help prevent HPV and cancer?

vaccine prevent infections and lowers cancer risk

what is the best method for preventing a viral disease?

vaccination

antiviral agents (HIV examples):

reverse transcriptase inhibitors, protease inhibitors, integrase inhibitors, fusion inhibitors