Heredity Unit 5

Question 1

Genetics

Answer 1

the study of heredity and heredity variation

Question 2

heredity

Answer 2

the transmission of traits from one generation to the next

Question 3

asexual vs sexual reproduction

Answer 3

asexual:
- single individual
- no fusion of gametes
- clones: offspring are exact copies of parent
- through mitosis
sexual:
- two parents
- offspring are unique combination of genes from parents
- genetically varied from parents and siblings

Question 4

Homologous chromosomes

Answer 4

a pair of chromosomes that carry the same genetic information

Question 5

_____ have DNA that is packaged in chromosomes

Answer 5

eukaryote

Question 6

what are autosomes

Answer 6

chromosomes that do not determine sex (humans have 22 pairs)

Question 7

fertilization

Answer 7

when a sperm cell (haploid) fuses an egg. (haploid) to form a zygote (diploid)

Question 8

meiosis

Answer 8

a process that creates haploid gamete cells in sexual reproducing diploid organisms
- results in daughter cells with half the number of chromosomes as the parent cell

Question 9

mitosis vs meiosis

Answer 9

mitosis:
-somatic cells, 1 division, results in 2 diploid daughter cells, daughter cells are genetically identically
meiosis:
forms gametes, 2 divisions, results in 4 haploid daughter cells, each daughter cell is genetically unique

Question 10

prophase I

Answer 10

• synapsis: homologous chromosomes pair up and connect to each other to form a tetrad.
• crossing over: occurs at the chiasmata and DNA is exchanged between homologous chromosomes.

Question 11

metaphase I

Answer 11

Independent orientation: tetrads line up at the metaphase plate

Question 12

anaphase I

Answer 12

homologous pairs separate
-sister chromatids are still attached

Question 13

telophase and cytokinesis I

Answer 13

• nuclei and cytoplasm divide
• now a haploid set of chromosomes in each daughter cell

Question 14

prophase II

Answer 14

-spindle forms

Question 15

metaphase II

Answer 15

• chromosomes line up at the metaphase plate
• chromatids are unique

Question 16

anaphase II

Answer 16

sister chromatids separate and move to opposite poles

Question 17

telophase and cytokinesis II

Answer 17

• 4 haploid cells
• nuclei will reappear
• each daughter cell is genetically unique

Question 18

genotype

Answer 18

the genetic makeup (alleles) for an organism

Question 19

phenotype

Answer 19

an organisms appearance which is determined by a genotype

Question 20

testcrosses help

Answer 20

determine whether if dominant trait is homozygous dominant or heterozygous

Question 21

principles of heredity

Answer 21

1. law of segregation
2. law of independent assortment

Question 22

allele

Answer 22

alternate form of a gene

Question 23

Mendel 4 concepts

Answer 23

1. Alternative versions of genes account for
   variations in inherited characteristics
2. For each character, an organism inherits
   two alleles of a gene, one from each parent.
3. If two alleles at a locus differ, then the dominant allele
   determines the appearance and the recessive allele
   has no noticeable effect
4. Law of segregation: the two alleles for the same trait
   separate during gamete formation and end up in
   different gametes

Question 24

law of segregation

Answer 24

the two alleles for the same trait separate during gamete formation and end up in different gametes

Question 25

Monohybrid crosses

Answer 25

a cross between the F1 hybrids

Question 26

law of independent assortment

Answer 26

genes for one trait are not inherited with genes of another trait - This law only applies to: genes that are located on different chromosomes (not homologous) OR genes that are very far apart on the same chromosome

Question 27

a heterozygous dyhybrid will produce what ratio?

Answer 27

Produces a 9:3:3:1 phenotypic ratio

Question 28

if a trait is x-linked then

Answer 28

males are more commonly affected than females

Question 29

Many traits do not follow the ratios predicted by Mendel's law why?

Answer 29

1. varying degrees of dominance 2. many traits are produced through multiple genes acting together 3. some traits are determined by genes on the sex chromosomes 4. some genes are adjacent or close to one another on the same chromosome and will segregate as a unit 5. some traits are a result of non-nuclear inheritance (chloroplast n mitochondria)

Question 30

incomplete dominance

Answer 30

- neither allele is fully dominant - F1 generation has a phenotype that is mix with the parental generation - ex: red with white will produce pink offspring

Question 31

codominance

Answer 31

- two alleles that affect phenotype are both expressed - human blood group - type AB blood- A and B are both expressed

Question 32

multiple alleles

Answer 32

genes that exist in forms with more than two alleles - human blood type- iA, iB, i

Question 33

epistasis

Answer 33

the phenotypic expression of a gene at one locus affects a gene at another locus - ex: coat color in labs and some mice

Question 34

sex linked genes

Answer 34

genes found on either x or y chromosome

Question 35

fathers can pass x linked alleles to all ____ but none of their ____ and mother can pass x linked alleles to _____

Answer 35

1. daughters, sons 2. both daughter and sons

Question 36

if an x-linked trait is due to a recessive allele.

Answer 36

1. females will only express trait is they're homozygous 2. Because males only have one X chromosome, they will express the trait if they inherit it from their mother ■ They are called hemizygous (since the term heterozygous does not apply) ■ Due to this males are much more likely to have an X-linked disorder

Question 37

name the 3 x-linked disorders

Answer 37

1. duchenne muscular dystrophy: progressive weakening of muscles 2. hemophilia: inability to properly clot blood 3. color blindness: inability to correctly see colors

Question 38

the inactive x in each cell of a female condenses into a __

Answer 38

Barr body (helps regulate gene dosage in females

Question 39

tay-sachs disease

Answer 39

- autosomal recessive disease - mutated HEXA gene - body fails to produce an enzyme that breaks down lipids - affects the nervous system and leads to blindness

Question 40

sickle cell anemia

Answer 40

- autosomal recessive disease - sickle cells contain abnormal hemoglobin molecules - mutated HBB gene

Question 41

non-disjunction

Answer 41

chromosomes are unable to separate properly during meoisis I or II - karyotypes can detect this ex: down syndrome: three copies of chromosome 21