Bio Ch. 13 Genes

Front 1

Gene

Back 1

Unit of heredity that encodes info for the form of a particular characteristics
-proteins

Front 2

Locus

Back 2

The location of a gene on a chromosome

Front 3

Homologous chromosomes

Back 3

Carry the same kinds of genes for the same characteristics
-Genes for the same characteristic are found at the same loci on both homologous chromosomes

Front 4

Alleles

Back 4

-Alternate versions or forms of genes found at the same gene locus
-Each carries two alleles per characteristic, one on each of the two homologous chromosomes

Front 5

Homozygous

Back 5

Both homologous chromosomes carry the same allele (gene form) at a given gene locus

Front 6

Heterozygous (hybrid)

Back 6

Two homologous chromosomes carry different alleles at a given locus

Front 7

Gregor Mendel

Back 7

-Czech Republic monk in late 1800s
-Botonist and mathematician
-Pea plant inheritance experiments (cross-fertilization, observing one trait at a time)

Front 8

Pea plants specifics

Back 8

-If homozygous for a particular characteristic, always produce the same physical forms
--Plants homozygous for a characteristic are True-Breeding
-Self-fertilize

Front 9

Genetic cross

Back 9

The mating of pollen and eggs (from same or different parents)

Front 10

Notation for Parental Generation:
First Filial Generation:
Second Filial Generation:

Back 10

...P
...F1
...F2

Front 11

Plant experiments specs

Back 11

1. Mendel crossed a true-breeding pruple flower plant with a true-breeding white-flower plant (P)
2. F1 generation consisted of all purple-flowered plants
3. Let F1 self fertilize: F2 had 1/4 white flowers
4.

Front 12

Genotype

Back 12

-Particular combination of the 2 alleles carried by an individual
-3 possibilities (PP, Pp, pp) (homo, hetero, homo)

Front 13

Phenotype

Back 13

Physical expression of the genotype (e.g. purple flowers)

Front 14

How Meiosis Separates Genes

Back 14

-Homologous chromosomes separate in meiosis anaphase I
-Each gamete receives one of each pair of homologous chromosomes and thus one of the two alleles per characteristic

Front 15

Mendel’s Law of Segregation

Back 15

Separation of alleles in meiosis

Front 16

How to bookkeep

Back 16

1. Add fractions of any genotypes of the same kind (1/4Pp + 1/4pP= 1/2Pp total)
2. From the sums of all the different kinds of offspring genotypes, create a genotypic ratio
1/4 PP, ½ Pp, ¼ pp is in the ratio 1PP: 2Pp: 1pp

Front 17

Test cross

Back 17

Used to deduce the actual genotype of an organism with a dominant phenotype (i.e., is the organism PP or Pp?)

Front 18

"Linked gene characteristics"

Back 18

-Different gene loci located on the same chromosome tend to be inherited together
-Characteristics whose genes tend to assort together are "linked"
-Messes up ratio in independent assortment; recombination increases variability also

Front 19

General thoughts on Mendel system

Back 19

Great for very simple situations, however doesn't work as things get more complicated (see
"linked")

Front 20

Autosomes

Back 20

Not sex chromosomes

Front 21

Genes carried on one chromosome are...

Back 21

Sex-linked.
-X is so much larger than Y chromosome; less in men to mask a bad recessive trait in Y

Front 22

X and U have very few genes in common, thus...

Back 22

-Females (XX) can be homozygous or heterozygous for a characteristic
-Males (XY) have only one copy of the genes on the X and Y

Front 23

Sex-linked (specifically X-linked) recessive alleles display their phenotype ___ often in males

Back 23

More

Front 24

Assumptions drawn from Mendel's Rules

Back 24

–All genes are governed by alleles found at a single locus on a pair of homologous chromosomes
–There are two alleles (gene forms) for each characteristic or gene type
–One allele is dominant over the other, which is recessive

Front 25

Incomplete dominance inheritance pattern

Back 25

-When the heterozygous phenotype is intermediate between the two homozygous phenotypes

Front 26

Multiple Allelism

Back 26

-Thousands of alleles for eye color in fruit flies, producing white, yellow, orange, pink, brown, or red eyes
–Human blood group genes producing blood types A, B, AB, and O
--Three alleles in this system: A, B, and O

Front 27

Codominance

Back 27

-Some alleles are always expressed even in combination with other alleles
--Heterozygotes display phenotypes of both the homozygote phenotypes

Front 28

Polygenic inheritance

Back 28

-Genes governed by the interaction of more than two genes at multiple loci
-Human skin color is controlled by at least 3 genes, each with pairs of incompletely dominant alleles

Front 29

Pleiotropy

Back 29

-Alleles of a characteristic may create multiple phenotypic effects
-Cascading effect

Front 30

Pedigree

Back 30

-Careful analysis of the diagram of records of gene expression over several generations of a family
-Reveals inheritance pattern of a trait

Front 31

Heterozygous individuals are _____ of a recessive genetic trait (but otherwise have a normal phenotype)

Back 31

carriers

Front 32

Tyrosinase

Back 32

enzyme that produces melanin

Front 33

Sickle-cell Anemia

Back 33

-A mutant hemoglobin gene causes hemoglobin molecules in blood cells to clump together
-Homozygous carriers face great difficulties
-Heterozygous carriers have great resistance to malaria, however

Front 34

Dominant Genetic Disorders

Back 34

-Affects heterozygous carriers as well, 50% in kids

Front 35

How dominant disease alleles disrupt normal cell functions:

Back 35

-Produce an abnormal protein that interferes with the function of the normal one
-Encode toxic proteins
-Encode a protein that is overactive or active at inappropriate times and places

Front 36

Sex-linked disorders

Back 36

appear more frequently in males and often skip generations

Front 37

Non-disjunction

Back 37

Incorrect separation of chromosomes or chromatids in meiosis

Front 38

Turner Syndrome

Back 38

(XO): an underdeveloped, infertile woman with only one X chromosome

Front 39

Trisomy X

Back 39

(XXX): a fertile, “normal” woman with an extra X chromosome

Front 40

Kleinfelter Syndrome

Back 40

(XXY): an infertile man with an extra X chromosome, having partial breast development and small testes

Front 41

XYY Male

Back 41

a tall man with an extra Y that produces high levels of testosterone and may score lower on IQ tests

Front 42

Trisomy 21

Back 42

(Down Syndrome) is an example of an abnormal autosomal number
-Down syndrome individuals have three copies of chromosome 21