3.3. Developmental, Quantitative, and Population Genetics

Question 1

understanding of developmental processes at the genetic level, such as (1) how genes mediate developmental events, and (2) how genes contribute to the continually changing phenotype of the newly formed organism

Answer 1

developmental genetics

Question 2

attainment of a differentiated state by all the cells of an organism, except for stem cells, wherein a cell achieve its final form and function

Answer 2

development

Question 3

how do cells shift from the undifferentiated to the differentiated state?

Answer 3

progressive activation of different gene sets in different cells of the embryo

Question 4

true or false : development relies on precise and coordinated programs of gene expression. this ensures that different cell types can develop specialized function, forming the tissues and organs of the organism.

Answer 4

true

during development, certain genes are turned on or off in a controlled and timely manner. this precise regulation is what allows cells to become specialized and form different tissues and organs

Question 5

describe variable gene activity hypothesis

Answer 5

suggests that differentiation is accomplished by activating and inactivating genes at different times in different cell types

differentiation is the process by which cells become specialized in their functions through activating/inactivating certain genes. this hypothesis explains how cells with the same genetic information can develop into diverse cell types with unique functions

Question 6

assumptions of variable gene activity hypothesis

Answer 6

(1) each cell contains an entire genome
(2) differential transcription of selected genes controls the development and differentiation of each cell

each cell in an organism has the full set of genetic information. the process of transcription is regulated differently in each cell type. in each type of cell, specific genes are transcribed into RNA and then into proteins, while others are not. for example, imagine you have a library (the genome) with all the books (genes). every cell in your body has a copy of this entire library. however, in a muscle cell, only the books (genes) needed to make muscles are read (transcribed), and in a nerve cell, only the books needed to make nerve cells are read. the rest of the books are still there but are not used in that particular cell type.

Question 7

these are used to study evolutionary conservation of developmental mechanisms

Answer 7

model organisms

examples of model organisms include Caenorhabditis elegans, Arabidopsis thaliana, and Drosophila melanogaster

Question 8

true or false : all animals use a common set of developmental mechanisms and signaling systems.

Answer 8

true

this ‘universality’ allows findings in model organisms to be relevant to a wide range of species

Question 9

true or false : model organisms share homology in genes and regulatory mechanisms.

Answer 9

true

model organisms share homologous genes with other species, meaning these genes have a common ancestor. for example, the gene that controls eye development in fruit flies is similar to the gene controlling eye development in humans. the mechanism that regulate gene expression are also often conserved. this means that studying how genes are turned on and off in model organisms can provide insights into gene regulation in other species

Question 10

true or false : fruit flies (drosophila melanogaster) follow the hierarchy of genes involved in establishing their segmented body plan

Answer 10

true

Question 11

discuss the hierarchy of genes in establishing the segmented body plan

Answer 11

(1) maternal-effect genes establish the anterior-posterior gradients that will guide the development of the embryo
(2) zygotic gap genes are activated by the gradients set up by maternal-effect genes and divide the embryo into broad regions
(3) zygotic pair-rule genes are activated by the gap genes. they further divide the embryo into segments, typically in pairs, which defines segment borders
(4) zygotic segment polarity genes refine the segmentation process by dividing each segment into anterior and posterior halves
(5) homeotic selector genes determine the identity of each segment. in drosophila, the hox genes determine whether a segment will develop into a part of the thorax, abdomen, or head.

Question 12

describe these drosophila developmental mutants :
(1) hunchback mutant
(2) Kruppel mutant
(3) knirps mutant

Answer 12

(1) hunchback mutant : lacks a head and thorx structures
(2) Kruppel mutant : lacks thorax and abdominal structures
(3) knirps mutant : lacks most abdominal structures

these mutants are evidences that genes control development. hunchback, kruppel and knirps are genes

Question 13

a mutation in humans that causes cleidocrania dysplasia (CCD), which is inherited in an autosomal dominant manner; individuals who have this mutation have holes on the top of their skulls as their fontanelles do not close; usually, their collar bones (clavicles) also do not develop. hence, they are capable of folding the shoulders across the chest

Answer 13

RUNX2 gene mutation

Question 14

a mutation in humans that causes synpolydactyly (SPD); individuals who have this mutations have extra fingers and toes. they also possess abnormalities in the bones of the hands and feet

Answer 14

HOXD13 gene mutation

Question 15

subfield of genetics that investigates the patterns of genetic variation within and among groups of interbreeding individuals

Answer 15

population genetics

how genes behave in a population

Question 16

what is a population?

Answer 16

group of individuals who (1) belong to the same species, (2) live in a defined geographic area, and (3) actually or potentially interbreeding

Question 17

all the genetic information carried by the members of a population

Answer 17

gene pool

Question 18

true or false : populations that are well adapted to their environment are homozygous.

Answer 18

false. most populations contain a high degree of heterozygosity. built-in genetic diversity is observed

Question 19

ways to detect genetic variation in a population

Answer 19

(1) nucleotide sequencing
(2) artificial selection

Question 20

is nucleotide sequencing a direct or indirect way to estimate genetic information?

Answer 20

it is a direct way to estimate genetic variation as it allows for the identification of differences between individual genomes by revealing the exact order of nucleotides in a DNA segment

Question 21

why is nucleotide sequencing significant?

Answer 21

enables us to detect variation in the nucleotide sequences of genes carried by individuals in a population

Question 22

oftentimes, individuals in a population posses a genomic variant at only a single base position in the DNA. how is this called?

Answer 22

single nucleotide polymorphism (SNP)

SNPs are single-base changes in the genome

Question 23

an indirect way of detecting gene variation in a population wherein a selection pressure is used to determine whether genetic variation exists in a population

Answer 23

artificial selection

artificial seletcion is considered indirect as the only parameter considered/observed in this process is phenotype. selection pressure are environmental or biological factors that determine which individuals (and their variations) are more likely to survive and reproduce

Question 24

true or false : in artificial selection, a phenotype affected by genetic variation will respond to selection and change over a few generations.

Answer 24

true

in artificial selection, a selection pressure is applied, and if a phenotype changes overtime, this means that the phenotype is affected by genetic variation. example : if a bacterium is grown in increasing concentrations of antibiotic, eventually, a strain of that bacterium will be produced as they adapt to the selection pressure

Question 25

describes what happens to alleles and genotypes in an “ideal population”

Answer 25

hardy-weinberg law

Question 25

who proposed the hardy-weinberg law?

Answer 25

godfrey hardy and wilhelm weinberg

Question 26

how is the hardy-weinberg law significant?

Answer 26

(1) helps establish the relationship between relative proportions of alleles in a gene pool and the frequencies of different genotypes in the population
(2) identifies causes of evolution in populations

Question 27

what makes a population “ideal”?

Answer 27

(1) infinitely large
(2) randomly mating
(3) not subjected to any evolutionary forces, such as selection, mutation, and migration

Question 28

two predictions of the hardy-weinberg model

Answer 28

(1) frequences of alleles in the gene pool are constant; they do not change over time
(2) after one generation of random mating, the frequencies of the genotypes in the population can be calculated as : p2 + 2pq + q2 = 1

Question 29

true or false : hardy-weinberg equilibrium is exhibited by a population that meets the hardy-weinberg ideal population criteria

Answer 29

true

Question 30

true or false : it is rare for a real population to conform totally to the hardy-weinberg model

Answer 30

true

Question 31

true or false : as a consequence of the hardy-weinberg law, dominant traits do not necessarily increase from one generation to the next

Answer 31

true

the presence of a dominant allele does not guarantee that its frequency will increase in the population over generations. the HWE shows that the allele frequencies will remain stable if no external forces act on the population. this challenges the common misconception that dominant traits will always become more common simply because they are dominant

Question 32

true or false : as a consequence of hardy-weinberg law, genetic variability can be maintained

Answer 32

true

in a stable environment where the three conditions of the Hardy-Weinberg equilibrium are met, allele frequencies remain constant. this stability contributes to the genetic diversity within a population, which is crucial for the adaptability and survival of species in changing environments.

Question 33

true or false : genotypic frequencies can be predicted due to hardy-weinberg law

Answer 33

true

the equation used to determine the genotypic frequencies is p2 + 2pq + q2 = 1

Question 34

study of quantitative inheritance wherein variations are measured and described in quantitative terms; relies on statistical analysis; e.g., human heights, milk production in cattle

Answer 34

quantitative genetics

Question 35

characteristics of quantitative inheritance

Answer 35

(1) multifactorial
(2) tend to show continuous variation
(3) polygenic

Question 36

quantitative genetics is characterized as multifactorial. what does this mean?

Answer 36

phenotypes result from (1) gene action, wherein the genotype generated at fertilization established a quantitative range within which a particular indiv. can fall, and (2) environmental influences or the factors that affect the final phenotype of an individual

human height, for example, is genetically influenced but is also affected by environmental factors such as nutrition

Question 37

quantitative genetics is characterized as continuous variation. what does this mean?

Answer 37

it has no distinct categories and often falls into a continuous range of phenotypes

more complex than doscontinuous variation

Question 38

quantitative genetics is characterized as polygenic. what does this mean?

Answer 38

varying phenotypes result from the input of genes at more than one, and often many, loci

Question 39

the multiple-gene hypothesis for quantitative inehritance proposed by william bateson and g. udny yule states that ___.

Answer 39

many genes, each individually behaving in a mendelian fashion, contribute to the phenotype in a cumulative or quantitative way

Question 40

what are the alleles in quantitative inheritance? differentiate them

Answer 40

(1) additive allele : contributes a constant amount to the phenotype; together the additive alleles contributing to a single quantitative character produce substantial phenotypic variation
(2) non-additive allele : does not contribute quantitatively to the phenotype