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Biology 111 > Week 4 > Flashcards

Week 4 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define: hierarchical gene expression

A

Genes expressed at each stage in the process control the expression of genes that act later.

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2
Q

Define: cellular blastoderm

A

In Drosophila development, the structure formed by the nuclei in the single-cell embryo when they migrate to the periphery of the embryo and each nucleus becomes enclosed in its own cell membrane.

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3
Q

Define: gastrulation

A

A highly coordinated set of cell movements in which the cells of the blastoderm migrate inward, creating germ layers of cells within the embryo.

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4
Q

Define: segmentation

A

The formation of discrete parts or segments in the insect embryo.

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5
Q

What are the three germ layers formed by gastrulation in humans and most other animals?

A
  1. ectoderm
  2. mesoderm
  3. endoderm
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6
Q

Define: oocyte

A

The unfertilized egg cell produced by the mother.

- matures under control of the mother’s genes

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7
Q

Define: maternal-effect genes

A

Genes that are expressed by the mother but affect the phenotype of the offspring.
NOTE: bicoid + nanos are maternal effect genes!

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8
Q

What does it mean when we say the egg is a highly polarized cell?

A

One end of the egg is distinctly different from the other.

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9
Q

Does the bicoid affect the anterior or posterior of the Drosophila?

A

Anterior

- mothers that are mutant for bicoid have larvae that lack anterior structures

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10
Q

Does the nanos affect the anterior or posterior of the Drosophila?

A

Posterior

- mothers that are mutant for nanos have larvae that lack posterior structures

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11
Q

Why are the levels of hunchback and caudal proteins localized to the anterior and posterior ends of the Drosophila embryo?

A

They are localized to each end because bicoid and nanos control the translation of the hunchback and caudal mRNA.

  • bicoid represses translation of caudal mRNA in the anterior
  • nanos represses translation of hunchback mRNA in the posterior
  • see figure 20.8
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12
Q

Would development happen normally if the mother has normal bicoid function, but the embryo does not? Why/why not?

A

Yes! Development would happen normally because bicoid is a maternal effect gene!!!

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13
Q

When does development start?

A

Development starts even BEFORE the zygote is formed, begins to occur in the oocyte.

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14
Q

Why can the genotype of the mother affect the phenotype of the developing embryo?

A

Because successful development of an embryo requires a functioning oocyte.

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15
Q

What gene(s) develop/set-up the anterior-posterior gradient?

A

Maternal Effect Genes

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16
Q

Which genes are the first to narrow down the anterior-posterior gradient?

A

Gap Genes

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17
Q

What do gap genes do?

A

Gap genes encode transcription factors that control genes in the next level of the regulatory hierarchy, which consists of pair-rule genes.

18
Q

What is one example of a gap gene in Drosophila and what is its function?

A

Krüppel

  • expressed in the middle region of the Drosophila embryo
  • responsible for development of thoracic and abdominal segments
19
Q

In order, what are the levels of genes that act on the development of the Drosophila?

A
  1. maternal-effect genes
  2. gap genes
  3. pair-rule genes
  4. segment-polarity genes
20
Q

Would the pattern of segment-polarity gene expression be normal if one or more gap genes were not expressed properly? Why/why not?

A

No, since each level of gene acts to refine the one before it… if the gap genes were not expressed properly, we can predict that the segment-polarity gene expression would not be normal.

21
Q

What is the role of homeotic (Hox) genes?

A

A homeotic gene is a gene that specifies the identity of a body part or segment during the embryonic development.
- expression of these genes are controlled by the segment-polarity genes and other genes expressed earlier on in the hierarchy

22
Q

What is an example of homeotic gene in Drosophila and what is its responsibility?

A

Antennapedia

- responsible for specifying the development of the leg

23
Q

Define: homeodomain

A

The DNA-binding domain in homeotic proteins, whose sequences are very similar from one homeotic protein to the next.

24
Q

What are three key observations of homeotic genes that have been seen in almost all organisms studied?

A
  1. correlation among linear order along the chromosome
  2. anterior-posterior position in the embryo
  3. timing of expression
25
Q

What are the differences/similarities between Drosophila and mammalian Hox genes?

A

Differences:
- in mammalians, do not specify limbs
Similarities:
- genes in each cluster are expressed according to their linear order along the chromosome

26
Q

Why is it difficult to learn exactly what each function of Hox genes are in mammalians?

A

Because they have redundant/overlapping functions.

27
Q

Define: loss-of-function mutation

A

A mutation that inactivates the normal function of a gene.

28
Q

Define: gain-of-function mutation

A

Any mutation in which a gene is expressed in the wrong place or at the wrong time.

29
Q

Define: downstream genes

A

A gene that functions later than another in development.

30
Q

Define: cis-regulatory element

A

A short DNA sequence adjacent to a gene, usually at the 5’ end, that interacts with transcription factors.

31
Q

Why does the mouse Pax6 gene induce the growth of eyes in Drosophila?

A

Master regulatory genes that control master development are often evolutionarily conserved, whereas the downstream genes can evolve new functions.
- downstream genes differ between the mouse and fruit fly but master regulatory gene (Pax6) remains the same - function of Pax6 is the same in all organisms (eye development)

32
Q

What is the key information that fossils/fossil records provide us with?

A
  • our only record of extinct species
  • calibrate phylogenies in terms of time
  • place evolutionary events in the context of Earth’s history
33
Q

What are two factors that determine the likeliness of a historic species being a part of the fossil record?

A
  1. properties of organisms (i.e. do they have a skeleton?)

2. environment (more likely if from the sea - was burial likely?)

34
Q

What are two ways that organisms without hard parts can develop a fossil record?

A
  1. trace fossils

2. molecular fossils

35
Q

Define: trace fossils

A

A track of trail, such as a dinosaur track or the feeding trails of snails and trilobites, left by an animal as it moves about or burrows into sediments.

36
Q

Define: molecular fossils

A

Sterols, bacterial lipids, and some pigment molecules, which are relatively resistant to decomposition, that accumulate in sedimentary rocks and document organisms that rarely form conventional fossils

37
Q

Define: burgess shale

A

A sedimentary rock formation in BC that preserves a remarkable sampling of marine life during the initial diversification of animals.

38
Q

Define: messel shale

A

A sedimentary rock formation in Germany, preserving fossils that document fish, birds, mammals, and reptiles from the beginning of the age of mammals.

39
Q

Define: geologic timescale

A

The series of time divisions that mark Earth’s history.

40
Q

How are we able to determine the age of archaeological samples?

A

Using radioactive dating - use various elements depending how old the fossil is.
- half-life

41
Q

Why is it important for us to know the age of fossils?

A

To provide calibration points for phylogenies.

42
Q

What is the effect of mass extinction on evolution?

A

Mass extinction essentially resents evolution.

- wipes out very large # of species

Biology 111 (4 decks)

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