Ch 15

Question 1

chromosome theory of inheritance

Answer 1

mendelian genes have specific loci (positions along the chromosome) and it is chromosomes that undergo segregation and independent assortment

Question 2

wild type fruit flies have what color eyes

Answer 2

red as opposed to white

Question 3

why are fruit flies great for genetic experiments

Answer 3

prolific breeders. only 4 chromosomes

Question 4

wild type

Answer 4

the phenotype for a character most commonly observed in natural poppulations

Question 5

notation for symbolizing fly alleles

Answer 5

w-white eyed, w+- red eyed

Question 6

mutant phenotypes

Answer 6

traits that are alternative of wild types, assumed to be mutations

Question 7

describe the white eyes in fruit flies

Answer 7

is recessive, located on X chromosome

Question 8

types of gender chromosomal systems

Answer 8

X-Y; mammals, gender depends on sperm
X-0; some insects, only X, male just one X; X0 females XX
Z-W; some birds, fishes insects, female determine Gender, females ZW, males ZZ
Haplo-diploid: bees and ants, no sex chromosomes, male 16 (haploid) and unfertilized, females 32 (diploid) fertilized

Question 9

signs of sex begin when

Answer 9

2 months, before that generic genitals

Question 10

sex linked gene

Answer 10

gene located on either sex chromosome

Question 11

Y-linked genes

Answer 11

genes located on Y chromosome, very few disorders are y-linked, most help determine sex

Question 12

X-linked genes

Answer 12

genes located on X chromosome, has genes for many characters unrelated to sex; color blindness is one and is recessive

Question 13

hemizygous

Answer 13

when referring to genes on male X chromosomes, it is not a pair, all genes (including recessive) will be , thus more X-linked disorders in males

Question 14

Duchenne muscular dystrophy

Answer 14

characterized by weakening of the muscles, X-linked gene

Question 15

Hemophilia

Answer 15

X-linked gene, poor blood clotting, common in European royalty

Question 16

Barr Body

Answer 16

inactive X-chromosome in females which lies along the inside of the nuclear envelope, reactivated in ovaries for gamete formation, choice occurs randomly and independently in each female embryotic cell

Question 17

females have a mosaic of

Answer 17

mixed X chromosome activate cells

Question 18

how is the X-chromosome deactivated

Answer 18

modification of the DNA and the histone proteins bound to it, including attaching of methyl groups (-CH3) to one of the nitrogenous bases of DNA nucleotides, a particular region of the X chromosome has genes for inactivation, the two regions of both chromosomes associate and then one of the genes called XIST (for X-inactive specific transcript) become active only on the chromosome which will become inactive, producing an RNA product which covers the X chromosome that produced it deactivating it

Question 19

linked genes

Answer 19

genes located near each other on the same chromosomes and tend to be inherited together during genetic crosses, thus said to be genetically linked

Question 20

genetic recombination

Answer 20

the production of offspring with combinations of traits that differ from those found in either parent

Question 21

parental type

Answer 21

offspring that match either of the parental (P generation) phenotypes

Question 22

recombinant type (recombinants)

Answer 22

phenotype matches neither parent due to combinations of traits

Question 23

crossing over

Answer 23

accounts for the recombination of linked genes, occurs while replicated homologous chromosomes are paired during prophase of Meiosis 1, a set of proteins orchestrates an exchange or corresponding segments of one maternal and one paternal chromatid. In effect, in effect end portions of two nonsister chromatids trade place each time a crossover occurs

Question 24

genetic map

Answer 24

an ordered list of the genetic loci along a particular chromosome

Question 25

the farther apart two genes are

Answer 25

the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency

Question 26

recombinant frequency

Answer 26

percentage of recombinant offspring, dependent on the distance between genes on a chromosome

Question 27

linkage map

Answer 27

genetic map based on recombinant frequencies (does not show actual distance between genes)

Question 28

map units

Answer 28

measurement to express differences between genes, equivalent to a 1% recombinant frequency (not physical difference)

Question 29

some genes which are physically connected (on same chromosome) are

Answer 29

genetically unlinked; because on opposite end of chromosome

Question 30

linkage groups

Answer 30

groups of linked genes

Question 31

cytogenetic map

Answer 31

locate genes with respect to chromosome features, such as stained bands

Question 32

nondisjunction

Answer 32

members of a pair of homologous chromosomes do not move apart properly during meiosis 1 or sister chromatids fail to separate during meiosis 2; one gamete receives tow of chromosome and another receives none

Question 33

aneuploidy

Answer 33

zygote has an abnormal number of a particular chromosome

Question 34

monosomic

Answer 34

chromosome missing

Question 35

trisomic

Answer 35

chromosome present in triplicate form

Question 36

polyploidy

Answer 36

some organism, fairly common in plants, more than two complete chromosome sets in all somatic cells, triploidy is 3 sets; nondisjunction of all its chromosomes, tetreaploidy is 4 sets; failure of 2n zygote to properly divide after chromosome replication

Question 37

deletion

Answer 37

chromosomal fragment is lost ( if centromere, whole chromosome lost) (especially likely to occur during meiosis)

Question 38

duplication

Answer 38

chromosomal fragment attaches as an extra segment to another chromosome, becomes a repeat in sister chromatids (especially likely to occur during meiosis)

Question 39

inversion

Answer 39

chromosomal fragment reattaches to original chromosome but in the reverse orientation

Question 40

translocation

Answer 40

fragment joins nonhomologous chromosome, common type is reciprocal, both side receive, less common is non reciprocal, only one side receives

Question 41

four results of chromosome breakage

Answer 41

deletion, duplication, inversion, and translocation

Question 42

Down syndrome

Answer 42

aneuploid condition, often called trisomy 21 due to extra chromosome 21, facial features, short stature, developmental delays, heart defects, increased chance of Alzheimer’s and leukemia, lower chance of high blood pressure, many types of tumors and arthritis. More common in older women

Question 43

XXY,XXX,X and XYY

Answer 43

XXY: Klinefelter syndrome, sterile, subnormal intelligence
XYY: normal but somewhat taller
XXX: at risk for learning disabilities and taller
X: Turner syndrome sterile

Question 44

cri du chat

Answer 44

severely disabled, small head, cries like cat, dies early in childhood, caused by deletion in chromosome 5

Question 45

chronic myelogenous leukemia

Answer 45

result of translocation, what would be white blood cells, chromosome 22, the Philadelphia chromosome

Question 46

genetic imprinting

Answer 46

(mostly on autosomes) gene expression varies based on which parent gave it, occurs during gamete formation when one gene is silenced, always imprinted same way generation after generation, result of methylation of DNA associated histones

Question 47

DNA in chloroplasts, mitochondria, and other plastids

Answer 47

transferred maternally, in egg cells, defects cause lower ATP, mitochondrial myopathy cause weakness, muscle intolerance and muscle deterioration, Leber’s hereditary neuropathy, causes blindness; 4 mutations found so far, may contribute to some heart disease and diabetes, also Alzheimer’s and aging