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Genetics > Chapter 4 > Flashcards

Chapter 4 Flashcards

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Biology 101 flashcards
1
Q

What are the Chromosomal Determinations used in sex determination?

A

XX-XO: XX female, XO male (grasshoppers)
XX-XY: XX female, XY male (mammals)
ZZ-ZW: ZZ male, ZW female (birds, snakes, butterflies, some amphibians, and some fish)

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2
Q

What is Homogametic sex?

A

Two of the sex-determining chromosomes—XX or ZZ, produce one type of gamete (all with X or all with Z)

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3
Q

What is Heterogametic sex?

A

Produces two different types of gametes (some with an X while some will have a Y in the case of XY organisms)

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4
Q

What are the Pseudoautosomal regions?

A

X and Y chromosomes are only homologous at the pseudoautosomal regions, which are essential for X-Y chromosome pairing in meiosis in the male (Primary and Secondary).

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5
Q

What is the SRY Gene?

A

One of the best characterized genes on the Y chromosome. Determines maleness.

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6
Q

How many genes are Y chromosomes and X chromosomes in a human?

A

In a Y chromosome, about 36 genes have been identified. In X chromosomes, about 1,100 genes have been identified.

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7
Q

What is drosophila and what is the genic balance system?

A

An X: A ratio in which X = number of X chromosomes and A = number of haploid sets of autosomes.

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8
Q

What is Genic Sex Determination?

A

-gene-level determination
-sex chromosomes determine the sex of the individual
(found in some plants, fungi, protozoans, and fish)

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9
Q

What is environmental determination?

A

A mechanism in which an individual’s sex is decided after conception, according to its immediate environment (factors like incubation temperature in some birds and reptiles).

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10
Q

What were Thomas Hunt Morgan’s experiments?

A

Experimenting with fruit flies and what the color of their eyes meant (red/white colored eyes)

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11
Q

What did Morgan suspect of the red/white eye color of fruit flies?

A

He suspected that eye color was a sex-linked characteristic (example of being carried on the X chromosome).

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12
Q

What contribution did Morgan make to sex-linked inheritance?

A

Discovered a mutant white-eyed male fly and traced its inheritance pattern, revealing a connection between the X sex chromosome and the gene for eye color. His work confirmed that genes are stored in chromosomes inside the cell nuclei.

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13
Q

What is sex-linked inheritance?

A

A biological process that involves the transmission of traits or characters from parents to offspring.

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14
Q

What inheritance patterns are expected with sex-linked genes?

A

X-linked characteristics and Y-linked characteristics. Males and females differ in sex chromosomes, so the pattern of inheritance is different from patterns observed for autosomes.

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14
Q

Why is drosophila a good Model Organism?

A

They’re easy and inexpensive to culture in a lab setting, they have a shorter life cycle, and they produce larger numbers of laid embryos that can be genetically modified.

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15
Q

What does hemizygous mean?

A

Having only a single copy of a gene instead of the customary two copies. All the genes on the single X chromosome in the male are ‘hemizygous (males are hemizygous).

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16
Q

What is x inactivation?

A

a process by which one of the copies of the X chromosome is inactivated in female mammals
(in mammals) occurs after several rounds of cell division and the formation of an embryo.
Also produces a staining inclusion in
the nucleus called a Barr body, which is a condensed, inactivated
X-chromosome (These should only be found in females).

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17
Q

What is a Barr body?

A

A condensed, inactivated
X-chromosome

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18
Q

How do you determine the number of Barr bodies with different numbers of chromosomes?

A

It’s one less than the total number of X chromosomes present.

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19
Q

What are Y-linked characteristics?

A

Only present in males, holandric traits, all male offspring will exhibit the trait, the Y chromosome lost DNA over time, and the SRY gene which is important for sex determination.

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20
Q

What are holandric traits?

A

Traits are only passed down from father to son. Only men have holandric traits, and they’re a Y-linked feature.

21
Q

What are the 3 Dominance patterns?

A
  1. Complete dominance
  2. Incomplete dominance
  3. Codominance
22
Q

What is complete dominance?

A

Hybrid resembles one of the two parents.

23
Q

What is incomplete dominance?

A

Hybrid resembles neither parent.

24
Q

What is codominance?

A

Hybrid shows traits from both parents.

25
Q

What is penetrance?

A

The percentage of individuals having a particular genotype that expresses the expected phenotype.

26
Q

What is expressivity?

A

The degree to which a character is expressed.

27
Q

What is pleiotropy?

A

The phenomenon of a single gene determining several distinct and seemingly unrelated characteristics.

28
Q

What are lethal alleles?

A

organisms that are homozygous for the
allele are dead

29
Q

What are multiple alleles?

A

for a given locus, more than two alleles are present within a group of individuals.

30
Q

What is ABO blood type an example of?

A

Multiple alleles. A child receives one of the three alleles from each parent, giving rise to six possible genotypes and four possible blood types (phenotypes)

31
Q

What are gene interactions?

A

Two (or more) genes influence a single trait.

32
Q

What is a novel phenotype?

A

A phenotype that is concerned with the visual appearance of an organism as compared to its parents (one type of gene interaction).

33
Q

What is epistasis?

A

One gene masks the effect of another gene.

34
Q

When a gene interaction has 4 distinct phenotypes, with a 9:3:3:1 ratio, what is implied?

A

That there is no epistasis.

35
Q

What is dominant epistasis?

A

when the dominant allele of one gene hides the expression of all alleles of another gene

36
Q

What is recessive epistasis?

A

when the recessive allele of one gene hides the expression of all alleles of another gene

37
Q

What is a complementation test, what is its purpose, and what is the meaning of the results?

A

Determines if mutations are occurring in the same or different loci.
Tests for determining whether two mutations associated with a specific phenotype represent two different forms of the same gene (alleles) or are variations of two different genes.
If the mutations are in the same gene then both copies of the gene will be mutant in the F1 offspring and they will exhibit the same phenotype as their parents

38
Q

What are sex-influenced characteristics?

A

autosomal traits that are influenced by sex

39
Q

What are sex-linked characteristics?

A

characteristics (or traits) that are influenced by genes carried on the sex chromosomes.

40
Q

What are sex-limited characteristics?

A

determined by genes located on autosomes and expressed only in one sex

41
Q

What is cytoplasmic inheritance?

A

Applies to organelles that have their own DNA (like the mitochondria and chloroplasts). Present in both males and females, usually inherited from one parent, typically the maternal parent, reciprocal crosses give different results and exhibit extensive phenotypic variation.

42
Q

What is the genetic maternal effect?

A

Genes expressed by mothers affect the phenotype of their offspring. Some diseases are inherited through mutations in the mitochondrial genes.

43
Q

What is genomic imprinting?

A

Caused by direct modifications of the DNA that prevent the expression of a particular gene.

44
Q

What is epigenetics?

A

“adjustment” of the DNA to promote or prevent expression of a gene.

45
Q

What is a temperature-sensitive allele?

A

An allele whose product is functional only at certain temperatures.

46
Q

What are 3 nutrional mutations?

A

-Phenylketonuria
-Galactosemia
-Lactose intolerance

47
Q

What is a discontinuous characteristic?

A

Relatively few phenotypes

48
Q

What is a continuous characteristic?

A

Continuous distribution of phenotypes; occurs when genes at many loci interact.

49
Q

What is polygenic inheritance?

A

Characteristics encoded by genes at many loci

50
Q

What is multifactorial inheritance?

A

The interaction of environmental and genetic determinants. More than 1 factor causes a trait or health problem.

Genetics (23 decks)

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