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ANSWERS:GENETICS

1.Study how genes bring about characteristics or traits in living things andthose characteristics are inherited.

2.A gene is a sequence of DNA nucleotides that codifies the production of aprotein.

3. It was developed by the Augustinian monk named Gregor Mendel.

4. -A gene is not a triplet of DNA nucleotides with their respective nitrogen-containing bases, like AAG or CGT. The nucleotide triplets may be pieces ofgenes but not genes. A gene is a portion of a DNA molecule that codifies aspecific protein. Thus it is formed by several DNA nucleotide triplets.

5 -A chromosome is a DNA molecule. A chromosome may contain several

different genes and also DNA portions that are not genes.

6-Gene locus (locus means place) is the location of a gene in a chromosome;the position of the gene in a DNA molecule.

7- This is alternative genes; it determines heritable traits.

8-A phenotype is every observable characteristic of a living being conditionedby its genes. Some phenotypes may be altered by non-genetic factors (forexample, artificial hair coloring). Specific phenotypes are also calledphenotypical traits.

9-Genotype is the genes, DNA nucleotide sequences contained in thechromosomes of an individual that condition the phenotype. Phenotypes thenare a biological manifestation of genotypes. For example, the alteredhemoglobin chain of sickle cell disease and the manifestation of the diseaseitself are the phenotype. The altered DNA nucleotide sequence in the genethat codifies the production of that abnormal hemoglobin chain is thegenotype.

1O-The environment can only alter genotypes when its action causesalterations in the genetic material (mutations) of the individual, i.e., deletion,

addition or substitution of entire chromosomes or of nucleotides that form theDNA molecules. Mutations are only transmitted to the offspring when affectingthe germ cells that produce gametes or the gametes themselves.

11- Heredity

12-Dominant allele is the allele that determines phenotypical features thatmanifest in homozygous or heterozygous genotypes.In Genetics the dominant

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allele is represented in uppercase, e.g., A, and its recessive allele is writtenin lowercase, a.In molecular terms generally the recessive allele has anucleotide sequencepreviously identical to the corresponding sequence in thedominant allele but that during evolution was inactivated by mutation. Thisfact explains the expression of the dominant phenotype in heterozygosity

(since one functional allele is still present).

13-Garden pea or Pisum Sativum.

14-Monohybrid crosses

15-Hybrids

16- Dihybrid

17- These are sex cells

18- Punnett Square

19- It state that members of a gene pair separate when the sperm and egg areformed.

20- It refers to a unit of heredity.

21- Genotype

22- Phenotype

23- Dominant allele

24- DNA or deoxyribonucleic acid

25- Mendel is considered the father of Genetics. He was a monk, biologist andbotanist born in Austria in 1822 and who died in 1884. During the years 1853to 1863 he cultivated pea plants in the gardens of his monastery to be used inhis research. His experiments consisted of crossing pea plants of distinctcharacteristics (size, color of the seeds, etc.), cataloging the results and

interpreting them. The experiments led him to enunciate his laws, resultspublished in 1886 with no scientific repercussion at that time. Only at thebeginning of the 20th century, in 1902, 18 years after his death, were hismerits broadly recognized.

26- Genetics is the crossing of individuals from pure and different lineages inrelation to a given trait; the crossing of different homozygous for the studiedtrait.

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27-The Mendels first law postulates that a characteristic (trait) of an individualis always determined by two factors, one inherited from the father and theother from the mother and the direct offspring of the individual receives fromit only one of these factors (aleatory). In other words, each trait is determinedby two factors that segregate during gamete formation.

28- These are flamentous structure in the cell nucleus, along which genes arelocated.

29- family tree is a schematic family tree that shows the biologicalinheritance of some trait through successive generations.

30 -Mendels second law states that gametes are formed always with analeatory representative of each pair of the factors that determine phenotypicalcharacteristics.Mendels second law is also known as the law of independent

segregation of factors, or law of independent assortment.

31-In the diploid genome of human beings there are 46 chromosomes,44 of them are autosomes and two are sex chromosomes. The individualinherits one of these chromosomes from each parent.The human sexchromosomes are called X chromosome and Y chromosome. Individualshaving two X chromosomes (44 + XX) are female. Individuals having oneX chromosome and one Y chromosome (44 + XY) are male. (Individuals44 + YY do not exist since the chromosome Y is exclusively frompaternal lineage.)

32-Homologous portion is that in which there are genes having alleles in bothY and X sex chromosomes. The homologous portions are situated more in thecentral part of the sex chromosomes, near the centromere. Heterologousportion is that whose genes do not have correspondent alleles in the other sexchromosome. These genes are located more in the peripheral regions of thearms of the Y and X chromosomes.

33- X-linked traits are phenotypical traits conditioned by genes located in thenonhomologous (heterologous) portions of the X chromosome.

34-Two genes are said to be under linkage, or linked, when they reside in the

same chromosome.For example, the research of the human genomediscovered that the factor III of clotting gene and the factor V of clotting geneare located in the same chromosome (the human chromosome 1). The factorVII gene however is not linked to those genes since it is located in thechromosome 13.

35-Genetic engineering is the use of genetic knowledge to artificiallymanipulate genes: It is one of the fields of biotechnology.

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