Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

BIOL 113 - Genetics > Week 11 > Flashcards

Week 11 Flashcards

1
Q

Who is the father of genetics

A

Mendel 1822-1884

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Who coined ‘genetics’

A

Bateson 1905

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Who coined the term ‘gene’

A

Johannsen 1909

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What did Mendel’s work lead to?

A

Worked with peas lead to:

  • Discovery of dominant and recessive traits
  • The concept of the ‘heritable factor’ (genes)
  • The formulation of the basic laws of inheritance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a monohybrid cross?

A

A cross between two true-breeding individuals differing in only one character

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is Mendel’s second law?

A

Law of independent assortment

“Each pair of alleles (gene) assorts independently of each other pair of alleles (gene) during gamete formation”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How was Mendel’s Law of Independent assortment formulated?

A

Formulated by following inheritance of 2 characters at the same time (involving parents differing in two characters - dihybrid cross)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What did Mendel observe when using monohybrid crosses?

A

All the F1 progeny resembled one of the parents, but both of the original parental traits appeared in the F2 generation

The ratio in the F2 was ~3:1

The same pattern of inheritance was seen for all 7 of the characters he studied.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What did Mendel conclude when using monohybrid crosses to study peas?

A

One trait is dominant and the other is recessive

The ‘heritable factor’ for the recessive trait had not been lost in the F1 - just masked by the presence of the factor for the dominant trait

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What did Mendel’s model show?

A

Variations in inherited characteristics are due to existence of alternative versions of heritable factors

For each character, an organism inherits two alleles; one from each parent

If two alleles differ, then the dominant allele determines the organisms appearance (phenotype)

Alleles do not blend when present in same individual, they remain discrete

Two alleles segregate during gamete formation and end up in different gametes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a character and trait according to Mendel?

A

Character is a heritable feature of an individual

Train is a variant form of a character (the phenotype)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the punnet square?

A

A diagrammatic device for predicting the outcomes of crosses between parents of known genotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Homozygous versus heterozygous example

A

Homozygous: GG or gg
Heterozygous: Gg

Highlights an important distinction between phenotype and genotype - different genotypes can produce the same phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the test cross?

A

A method for determining the genotype of an individual with the dominant phenotype of a trait

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

When solving more complex genetic problems for example triple heterozygote, we use what?

A

Probabilities.

Deal with each of the three allele pairs separately in punnet squares and multiply the probabilities together to give the overall probability.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Sutton wrote what in his 1902 paper that gave evidence Mendelian law was correct?

A

The association of paternal and maternal chromosomes in pairs and their subsequent separation during the reduction division may constitute the physical basis of the Mendelian law of heredity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Mitosis versus Meiosis: Where does the process occur?

A

Mitosis - in somatic cells
Meiosis - in germ line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Mitosis versus Meiosis: How many cells are produced?

A

Mitosis = 2 identical diploid cells
Meiosis = 4 non-identical haploid cells (gametes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Mitosis versus Meiosis: Synapsis?

A

Synapsis is unique to meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Mitosis versus Meiosis: Roles?

A

Mitosis = Growth and tissue repair

Meiosis = Produce haploid gametes and to introduce genetic variability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a chromatid?

A

One of the two identical strands of a newly replicated chromosome
(not to be confused with the pair of homologous chromosomes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are sister chromatids?

A

Two identical chromatids held together by a common centromere following replication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Mendelian inheritance has its physical basis in the behaviour of what during meiosis

A

Chromosomes

Sutton made the link between the behaviour of chromosomes during meiosis and Mendel’s Laws

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What did Sutton observe?

A
  • Chromosomes occur in pairs in somatic cells
  • Chromosome pairs segregate equally into gametes
  • Different chromosome pairs assort independently

He reasoned if chromosomes carried genes, this behaviour would explain Mendel’s observations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What does the chromosome theory of inheritance state?
Mendel's 'inheritable factors' (or genes) are located at specific positions (loci) on chromosomes It is the chromosomes that undergo segregation and independent assortment
26
How does chromosome behaviour in meiosis explain Mendel's Law of Segregation?
"Two forms of a gene present in each parent segregate independently" because each allele is on a different member of a homologous pair of chromosomes and moves to opposite poles in anaphase I
27
What does the independent assortment of chromosomes mean?
Each of the 4 possible combinations of alleles at the two loci has an equal probability of occurrence in the gametes.
28
What are the sources of genetic variability in sexual life cycles?
Mutation Independent assortment Crossing-Over Random fertilization
29
Why is there less recombination when genes are on the same chromosome?
Crossing over has to occur, which is irregular
29
What is a recombinant phenotype?
The combination of phenotypes differs from that found in either of the parents
30
How do recombinant phenotypes occur?
Through either: - Independent assortment (genes on different chromosomes) - Crossing over (genes on the same chromosome)
31
What is crossing over?
The process of genetic recombination that gives rise to new combinations of linked genes
32
Crossing over occurs in what phase of meiosis?
The pachytene phase of prophase I It begins with synapsis (pairing of homologous chromosomes)
33
What is the synaptonemal complex (crossing over)?
A protein 'zipper' that holds homologous chromosomes together in the tetrad
34
What leads to crossing over between homologous chromosomes?
Formation of the synaptonemal complex
35
What is the result of crossing over?
Recombinant chromosomes with new combinations of linked genes and therefore alleles
36
What is recombination frequency?
The % of the progeny that inherit a combination of alleles that differs from either parent
37
How do you calculate recombination frequency?
(Number of recombinants / Total number of progeny) x 100%
38
How are recombination frequencies estimated?
By studying the results of a testcross The recombination frequency between two genes depends on whether the genes are on the same or on different chromosomes. For genes on different chromosomes, the recombination frequency will be 50%
39
Who first observed gene linkage? Using what?
T.H.Morgan (1866-1945) He studied vestigial wing mutant of Drosophila melanogaster (fruit fly)
40
What symbol is written when a phenotype reflects the normal allele (wild-type)?
+ sign
41
What are the two possible arrangements of alleles in a double heterozygote?
Coupling heterozygote and Repulsion heterozygote This will affect the outcome of a testcross with the double mutant
42
What did A.H. Sturtevant realise in 1913?
Information on using recombination frequencies could be used to make chromosome linkage maps (He saw that the recombination frequency between two genes should be related to their distance apart on the chromosome)
43
What is a two-point cross?
Double heterozygote crossed with double recessive
44
Why doesn't chromosome linkage map distance add up?
Multiple crossovers could have occurred: - Lead to an underestimate of distance between two loci - Means recombination frequencies >50% are not possible - Genes far apart on the same chromosome appear to assort independently
45
Large numbers on mapping genes always indicate the _____ type, and the smallest numbers are the result of a _______ _______
Parental, Double crossover
46
What are the 6 deviations from Mendelian ratios?
Sex-linkage Incomplete dominance Co-dominance Pleiotropy Polygenic inheritance Epistasis
47
Where was sex-linkage inheritance first observed?
In drosophila (flies)
48
What is incomplete dominance?
Where a dominant allele does not completely mask the effect of a recessive allele at the same locus
49
What is an example of incomplete dominance in humans?
Familial Hypercholesterolaemia
50
What is co-dominance?
Where each allele affects the phenotype in separate, distinguishable ways
51
Compare incomplete dominance and co-dominance?
Incomplete: Blending of traits and a 'diluted' phenotype Co-: No blending; traits appear together and remain distinct in the heterozygote
52
What is Pleiotropy?
Where a single gene has multiple effects on the phenotype. (Many human diseases that are caused by single gene mutations have pleiotropic effects eg sickle cell)
53
What is polygenic inheritance?
Where a single trait is determined by multiple genes eg height in humans, weight, skin pigmentation, etc.
54
What is epistasis?
When one gene masks or modifies the expression of another gene
55
What is cytogenetics?
The study of the structure and function of chromosomes (Used for the screening and diagnosis of inherited chromosomal disorders)
56
What is a karyotype? What is the human male karyotyoe?
A karyotype is a preparation of chromosomes arranged in size order A human male karyotype is 2n = 46
57
In what 3 ways does karyotyping identify a chromosome?
Length Banding pattern Placement of centromere
58
What are the three different locations a centromere can be found known as?
Metacentric (centre) Sub-metacentric (off-centre) Acrocentric (very close to end)
59
What two reasons is karyotyping used?
To detect changes in chromosome number and structure
60
What is polyploidy? (uses of karyotyping: changes in chromosome number)
Extra whole sets of chromosome eg triploid, tetraploid, etc
61
What is aneuploidy (uses of karyotyping: changes in chromosome number)
Some additional or missing chromosomes eg Monosomy (one missing chromosome) or Trisomy (one extra chromosome)
62
What is the cause of aneuploidy?
Non-disjunction of homologous chromosomes in meiosis I Non-disjunction of sister chromatids in meiosis II
63
What is the only autosomal aneuploidy that permits survival into adulthood? How common is aneuploidy?
Down's Syndrome Very common, it occurs in 50% of human conceptions
64
What does Trisomy on chromosome 21 lead to?
Down's syndrome
65
What are characteristics of Down's Syndrome
Characteristic facial features, Short stature, Some level of learning disability, Heart defects, Susceptibility to leukaemia and Alzheimer's disease
66
Incidence of Down's syndrome increases with _______ age?
Maternal
67
How are chromosomal abnormalities screened for?
1. Blood tests (to detect specific proteins associated with a Down's foetus) 2. Ultrasound scans (to measure the size of the nuchal pad at the nape of the foetal neck associated with Down's Syndrome) 3. Amniocentesis and karyotyping
68
What chromosome does Turner's Syndrome occur on?
45 (XO)
69
What are characteristics of Turner's syndrome?
Phenotypically female, Sterile due to lack of maturation of sex organs Oestrogen replacement therapy leads to development of secondary sex characteristics
70
What chromosome is Klinefelter's syndrome associated with?
47, XXY (One of the most common genetic abnormalities)
71
Characteristics of Klinefelter's Syndrome?
Essentially male but with some female characteristics Tall stature Sterile Treated with hormone replacement therapy (testosterone)
72
What chromosome determines biological sex?
The presence or absence of the Y chromosome
73
What are the 4 ways chromosomes can mutate?
Deletion, Duplication, Inversion, Reciprocal translocation
74
Why is each G-band on a chromosome given an 'address'?
Allows specific chromosomal mutations to be accurately described
75
What are examples of Syndromes that occur when deletion mutation happens on a chromosome?
Cri-du-chat Syndrome (Deletion of part of short arm of Chr 5) Prader-Willi Syndrome / Angelman Syndrome (Deletion in long arm of Chro 15)
76
Characteristics of Cri-Du-Chat syndrome?
Babies have cat-like cry Defects in glottis and larynx Wide face with saddle nose Physical and intellectual disability Range of severity, depending on the extent of the deletion
77
What are characteristics of Prader-Willi's Syndrome?
Poor suckling reflex in infants, Uncontrollable eating in later life, Obesity, Diabetes, Poor sexual development in males, Only occurs when the affected chromosome is inherited from the father to do genomic imprinting
78
What is genomic imprinting?
The process that affects certain genes, whereby either the maternal or paternal copy of the gene is silenced
79
Angelman's Syndrome arises from what?
If the same segment is missing from the maternally derive chromosome 15 (because the imprinted genes on the other chromosome are different in each case)
80
What are characteristics of Angelman's syndrome?
Happy demeanour, Inappropriate outbursts of laughter, Intellectual disability, Severe speech problems, Stiff limb movements, Seizures
81
What are examples of Syndromes that occur when translocations mutation happens on a chromosome?
Familial Down's Syndrome: t(14;21) Chronic myelotic leukaemia: t(22;9)
82
What chromosome does Familial Down's Syndrome occur on?
Translocation carrier t(14;21): One of the Chr 21's is attached to one of the chr 14s
83
What is the chance of Familial Down's Syndrome affecting the second child of parents?
1:3
84
Is chronic myelocytic leukaemia (CML) inheritable?
No, it occurs spontaneously. Occurring in 1 per 50-100,000 of the population
85
95% of people with Chronic myelocytic leukaemia also have what chromsoeome?
The Philadelphia chromosome
86
What chromosome does chronic myelocytic leukaemia occur on?
22-9 translocation
87
How does chronic myelocytic leukaemia occur?
Translocation creates the BCR-ABL fusion gene (an oncogene that stimulates over-production of WBC) Accounts for 15-20% of all cases of leukaemia!
88
Making a karyotype step 1?
- Draw 10-20 ml of blood, add to a culture flask containing growth medium and add phytohaemagglutinin to stimulate mitosis - Incubate for 2-3 days
89
Making a karyotype step 2?
- Treat with colcemid for 1-2 hrs to stop mitosis in metaphase, transfer cells to a tube
90
Making a karyotype step 3?
- Pellet cells by centrifugation, add hypotonic solution to lyse cells and transfer to tube containing fixative
91
Making a karyotype step 4?
Drop cells onto microscope slide, stain with Geisma
92
Making a karyotype step 5?
- Examine with microscope, photograph metaphases. - Arrange chromosomes into a karyotype
93
Give an example of an aneuploidy condition in humans caused by trisomy on chr 18?
Edwards Syndrome
94
What is Amniocentesis? (Screening for chromosomal abnormalities)
Drawing amniotic fluid from the uterus and culturing the cells before karyotyping to give a proper diagnosis of Down's Syndrome
95
What letters are used to symbolise a chromosome short arm and long arm?
Short arm = p Long arm = q

BIOL 113 - Genetics (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions